Methods and devices for preserving tissues

ABSTRACT

Methods and apparatus for preserving detached tissues, especially digits and limbs, which are detached as a result of traumatic amputation. By using the methods and apparatus, detached tissues can be preserved for greater lengths of time and are ultimately in a better condition for replantation surgery.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/420,962 filed Mar. 15, 2012, which claims priority to U.S.Provisional Application Ser. No. 61/541,425, filed Sep. 30, 2011, andU.S. Provisional Application Ser. No. 61/452,917, filed Mar. 15, 2011,all of which are incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The invention relates to methods and devices for storing, preserving,and transporting tissues, such as organs, grafts, and severed digits orlimbs, such as from a traumatic amputation.

BACKGROUND

Recent advances in microsurgery have greatly increased the success ratefor replantation surgery following amputation, e.g., traumaticamputation. Whereas two decades previously it was newsworthy when asevered limb was successfully reattached, replantation of fingers,hands, arms, ears, feet, and toes now happens with regular frequency. Inparticular, severed fingers are commonly replanted with a reattachmentsuccess rate of about 87%. Remarkably, in over half of the digitreplantation procedures the patient eventually recovers full function ofthe digit. See Zumiotti et al., “Replantation of digits: factorsinfluencing survival and functional results.” Microsurgery 1994;15(1):18-21.

Of course, not all traumatic amputations are candidates forreplantation. If the limb (or digit) is crushed, or the amputation is ina location where reattachment is not practical (e.g., thigh),replantation is not attempted.

In the event of a “guillotine” injury, however, in which the limb ordigit is cleanly separated from the body, replantation is oftenattempted. In these cases, the most determinative factor of the eventualoutcome of replantation is the condition of the body part when itarrives to the operating room. Severed limbs and digits that are cleanand kept cold are more likely to result in a good outcome. Despiteadvances in tissue preservation, the standard of care for preservationof separated tissues (e.g., limbs, digits) has not changed substantiallyover the last twenty years. Most first responders (e.g., EMS,paramedics) are currently equipped with amputation kits that are merelysterile counterparts to the preservation method of placing the body partin a bag and putting the bag with the body part on ice until reachingthe hospital. Once at the hospital, the separated tissues may bepreserved in a sterile refrigerator, or other specialized equipment,until the patient is ready for replantation surgery.

While anecdotes of longer separation times are known, replantation istypically not recommended after 12 hours of warm or 24 hours of coldischemia for digits, and 6 hours of warm or 12 hours of cold ischemiafor major replants (e.g. limbs). A portable preservation apparatus whichwould increase the allowable time between detachment and replantationwould likely improve outcomes after traumatic-amputation. Such a systemcould be used by medical flight crews, EMS teams, and combat paramedics.Such a system would be especially useful in combat zones where anamputee may have to wait hours to be evacuated, or will have asubstantial transit time to reach a surgical facility.

SUMMARY OF THE INVENTION

The invention discloses methods and apparatus for preserving detachedtissues, especially digits and limbs, which are detached as a result oftraumatic amputation. By using the methods and apparatus, detachedtissues can be preserved for greater lengths of time and are ultimatelyin a better condition for replantation (i.e., reattachment) surgery.Thus, the methods and apparatus of the invention will result in improvedoutcomes for victims of amputation, e.g., traumatic amputation.

The methods of the invention involve storing and/or transporting thesevered tissue in a container in the presence of a preservation fluid,typically a pressurized, oxygenated preservation fluid. The containermay additionally provide a time varying pressure greater thanatmospheric pressure on the preservation fluid, thereby simulating forthe interior tissues (muscles, nerves, etc.) a pressure environmentanalogous to that experienced when the tissue was attached. In someinstances, the container will be kept at a hypothermal temperature inorder to better preserve the tissue. In some instances the preservationsolution will contain nutrients and/or electrolytes.

In one instance, an apparatus of the invention is configured tooxygenate and perfuse the detached tissue. The apparatus may alsomonitor the health of the tissue by measuring parameters such as oxygenconsumption. The apparatus includes a pneumatic system, a pumpingchamber, and a tissue chamber. The pneumatic system is configured forthe controlled delivery of fluid to and from the pumping chamber basedon a predetermined control scheme. The predetermined control scheme canbe, for example, a time-based control scheme or a pressure-based controlscheme. The pumping chamber may additionally be configured to diffuse agas into a perfusate and to generate a pulse wave for moving theperfusate through the tissue.

In some instances, the preservation apparatus is configured tosubstantially automatically purge excess fluid from the tissue chamberto the pumping chamber. The pumping chamber may then, in turn, beconfigured to self-purge excess fluid from the pumping chamber to anarea external to the apparatus. For example, the pumping chamber,disposed in the lid assembly, may be separated into first and secondportions by a membrane, and the membrane disposed so that rising fluidwill be directed to a highest point and then out of the container, forexample, through a purge port.

Thus, using the methods and apparatus of the invention it is possible totransport and preserve severed tissue, thereby improving outcomes ofreplantation surgery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an apparatus according to anembodiment.

FIG. 2 is a perspective view of an apparatus according to an embodiment.

FIG. 3 is a side view of the apparatus of FIG. 2.

FIG. 4 is a cross-sectional view of the apparatus of FIG. 2 taken alongline Y-Y, with a portion of a pneumatic system removed.

FIG. 5 is a cross-sectional view of a lid assembly of the apparatus ofFIG. 2 taken along line X-X (shown in FIG. 3).

FIG. 6 is an exploded perspective view of a lid assembly of theapparatus of FIG. 2.

FIG. 7 is a top view of a portion of a lid assembly and a pneumaticsystem of the apparatus of FIG. 2.

FIG. 8 is a schematic illustration of a pneumatic system and a pumpingchamber of the apparatus of FIG. 2.

FIG. 9 is a schematic illustration of a pneumatic system and a pumpingchamber of an apparatus according to an embodiment.

FIG. 10 is a front perspective view of an apparatus according to anembodiment.

FIG. 11 is a rear perspective view of the apparatus of FIG. 10.

FIG. 12 is a front perspective view of the apparatus of FIG. 10 with thelid cover, one of the clamps, and the tissue chamber removed.

FIG. 13 is a side view of the apparatus of FIG. 10.

FIG. 14 is a cross-sectional view of the apparatus of FIG. 10 takenalong line W-W (shown in FIG. 10).

FIG. 15 is a cross-sectional view of the apparatus of FIG. 10 takenalong line V-V (shown in FIG. 13).

FIG. 16A is an enlarged cross-sectional view of the portion of FIG. 14identified by the line 16A.

FIG. 16B is an enlarged cross-sectional view of a portion of anapparatus according to an embodiment.

FIG. 17 is a component diagram of a control system according to anembodiment.

FIG. 18 is a flow diagram of a method for calculating flow rate andresistance according to an embodiment.

FIG. 19 is a perspective view of an apparatus according to anembodiment.

FIG. 20 is a cross-sectional view of the apparatus of FIG. 19 takenalong line U-U (shown in FIG. 19).

FIG. 21A is a cross-sectional view of a lid assembly of the apparatus ofFIG. 19 taken alone line T-T (shown in FIG. 19).

FIG. 21B is an enlarged cross-sectional view of a portion of the lidassembly of the apparatus of FIG. 21A.

FIG. 22 is a top perspective view of a portion of the lid assembly ofthe apparatus of FIG. 19.

FIG. 23 is a side perspective view of the portion of the lid assembly ofFIG. 22.

FIG. 24 is a cross-sectional view of the portion of the lid assembly ofFIG. 22 taken along line S-S (shown in FIG. 22).

FIG. 25 is a top perspective view of a portion of the lid assembly ofthe apparatus of FIG. 19.

FIG. 26 is a bottom perspective view of the portion of the lid assemblyof FIG. 25.

FIGS. 27A-27C are bottom perspective views of the lid assembly, acoupling mechanism, and a canister of the apparatus of FIG. 19 in afirst configuration, a second configuration, and a third configuration,respectively.

FIGS. 28A-28C are top perspective views of the lid assembly and thecoupling mechanism of the apparatus of FIG. 19 in a first configuration,a second configuration, and a third configuration, respectively.

FIG. 29 is a front view of the canister of the apparatus of FIG. 19.

FIG. 30 is a front view of a canister according to an embodiment.

FIG. 31 is a perspective view of the canister of FIG. 30 and a tissue.

FIG. 32 is a perspective view of the apparatus of FIG. 19.

FIG. 33 is a front view of a carrier assembly for use with the apparatusof FIG. 19.

DETAILED DESCRIPTION

Devices, systems and methods are described herein that are configured tooxygenate and/or perfuse tissues for the extracorporeal preservation ofthe tissue. More specifically, described herein are devices, systems,and methods that are configured to oxygenate a perfusate and to perfuse(bathe) the tissue with the oxygenated perfusate in a portable device,thereby extending the viability of the tissue over a longer period oftime. Such extracorporeal preservation of tissue is desirable, forexample, for transportation of severed tissues, e.g., as a result oftraumatic amputation.

In some embodiments, a device is configured to self-purge excess fluid(e.g., liquid and/or gas). For example, in some embodiments, a deviceincludes a lid assembly in which at least a portion of the lid assemblyis inclined with respect to a horizontal axis. The inclined portion ofthe lid assembly is configured to facilitate the flow of fluid towards apurge port disposed at substantially the highest portion of a chamber ofthe lid assembly. In this manner, excess fluid can escape the device viathe purge port. Also in this manner, when excess liquid is expelled fromthe device via the purge port, an operator of the device can determinethat any excess gas has also been purged from the device, or at leastfrom within a tissue chamber of the device, because the gas is lighterthan the liquid and will move towards and be expelled via the purge portbefore excess liquid.

In some embodiments, a device is configured to pump oxygen through apumping chamber to oxygenate a perfusate and to perfuse a tissue basedon a desired control scheme. For example, in some embodiments, thedevice includes a pneumatic system configured to deliver oxygen to thepumping chamber on a time-based control scheme. The pneumatic system canbe configured to deliver oxygen to the pumping chamber for a firstperiod of time. The pneumatic system can be configured to vent oxygenand carbon dioxide from the pumping chamber for a second period of timesubsequent to the first period of time. In another example, in someembodiments, the device includes a pneumatic system configured todeliver oxygen to the pumping chamber on a pressure-based controlscheme. The pneumatic system can be configured to deliver oxygen to thepumping chamber until a first threshold pressure is reached within thepumping chamber. The pneumatic system can be configured to vent oxygenand carbon dioxide from the pumping chamber until a second thresholdpressure is reached within the pumping chamber. In some embodiments, apower source of the device is in use when oxygen is being delivered tothe pumping chamber and is not in use when oxygen and carbon dioxide arebeing vented from the pumping chamber. In this manner, the device isconfigured to help minimize usage of the power source, and thus thedevice can prolong the period of time a tissue is extracorporeallypreserved within the device before the power source is depleted. Such animprovement increases the time available for transporting the tissue toa hospital for replantation.

In another embodiment, the invention includes a method for preservingsevered tissue during transport. The method includes placing a severedtissue in a portable container and perfusing the severed tissue with anoxygenated preservation fluid at a pressure greater than atmosphericpressure during transport. With this method, the preservation fluid isoxygenated and pressurized by a pumping chamber that is disposed in alid assembly of the container, and the container is capable ofself-purging a fluid from the portable container. In one instance, thelid assembly defines the pumping chamber and the pumping chambercomprises a semi-permeable membrane dividing the pumping chamber into afirst portion and a second portion, wherein the membrane is disposedwithin the lid assembly at an angle such that the membrane can direct arising fluid in the second portion of the pumping chamber toward ahighest point. A purge point may be in fluid communication with thehighest point.

As used in this specification, the singular forms “a,” “an” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, the term “a fluid” is intended to mean a single fluidor a combination of fluids.

As used herein, “a fluid” refers to a gas, a liquid, or a combinationthereof, unless the context clearly dictates otherwise. For example, afluid can include oxygen, carbon dioxide, or another gas. In anotherexample, a fluid can include a liquid. Specifically, the fluid can be aliquid perfusate. In still another example, the fluid can include aliquid perfusate with a gas, such as oxygen, mixed therein or otherwisediffused therethrough.

As used herein, “tissue” refers to any tissue of a body of a patient,including tissue that is suitable for being replanted or suspected ofbeing suitable for replantation. Tissue can include, for example, muscletissue, such as, for example, skeletal muscle, smooth muscle, or cardiacmuscle. Specifically, tissue can include a group of tissues forming anorgan, such as, for example, the skin, lungs, cochlea, heart, bladder,liver, kidney, or other organ. In another example, tissue can includenervous tissue, such as a nerve, the spinal cord, or another componentof the peripheral or central nervous system. In still another example,tissue can include a group of tissues forming a bodily appendage, suchas an arm, a leg, a hand, a finger, a thumb, a foot, a toe, an ear,genitalia, or another bodily appendage.

An apparatus 10 according to an embodiment is schematically illustratedin FIG. 1. The apparatus 10 is configured to oxygenate a perfusate (notshown) received in a pumping chamber 14 of the apparatus. The apparatus10 includes a valve 12 configured to permit a fluid (e.g., oxygen) to beintroduced into a first portion 16 of the pumping chamber 14. A membrane20 is disposed between the first portion 16 of the pumping chamber 14and a second portion 18 of the pumping chamber. The membrane 20 isconfigured to permit the flow of a gas between the first portion 16 ofthe pumping chamber 14 and the second portion 18 of the pumping chamberthrough the membrane. The membrane 20 is configured to substantiallyprevent the flow of a liquid between the second portion 18 of thepumping chamber 14 and the first portion 16 of the pumping chamberthrough the membrane. In this manner, the membrane can be characterizedas being semi-permeable.

The membrane 20 is disposed within the pumping chamber 14 along an axisAl that is transverse to a horizontal axis A2. Said another way, themembrane 20 is inclined, for example, from a first side 22 to a secondside 24 of the apparatus 10. As such, as described in more detail below,a rising fluid in the second portion 18 of the pumping chamber 14 willbe directed by the inclined membrane 20 towards a port 38 disposed atthe highest portion of the pumping chamber 14. The port 38 is configuredto permit the fluid to flow from the pumping chamber 14 into theatmosphere external to the apparatus 10. In some embodiments, the port38 is configured for unidirectional flow, and thus is configured toprevent a fluid from being introduced into the pumping chamber 14 viathe port (e.g., from a source external to the apparatus 10). In someembodiments, the port 38 includes a luer lock.

The second portion 18 of the pumping chamber 14 is configured to receivea fluid. In some embodiments, for example, the second portion 18 of thepumping chamber 14 is configured to receive a liquid perfusate. Thesecond portion 18 of the pumping chamber 14 is in fluid communicationwith an adapter 26. The adapter 26 is configured to permit movement ofthe fluid from the pumping chamber 14 to a tissue T. For example, insome embodiments, the pumping chamber 14 defines an aperture (not shown)configured to be in fluidic communication with a lumen (not shown) ofthe adapter 26. The adapter 26 is configured to be coupled to the tissueT. The adapter 26 can be coupled to the tissue T in any suitable manner.For example, in some embodiments, the adapter 26 is configured to besutured to the tissue T. In another example, the adapter 26 iscoupleable to the tissue T via an intervening structure, such assilastic or other tubing. In some embodiments, at least a portion of theadapter 26, or the intervening structure, is configured to be insertedinto the tissue T. For example, in some embodiments, the lumen of theadapter 26 (or a lumen of the intervening structure) is configured to befluidically coupled to a vessel of the tissue T.

In some embodiments, the adapter 26 is configured to support the tissueT when the tissue T is coupled to the adapter. For example, in someembodiments, the adapter 26 includes a retention mechanism (not shown)configured to be disposed about at least a portion of the tissue T andto help retain the tissue T with respect to the adapter. The retentionmechanism can be, for example, a net, a cage, a sling, or the like. Insome embodiments, the apparatus 10 includes a basket (not shown) orother support mechanism configured to support the tissue T when thetissue T is coupled to the adapter 26 or otherwise received in theapparatus 10.

A tissue chamber 30 is configured to receive the tissue T and a fluid.In some embodiments, the apparatus 10 includes a port 34 that isextended through the apparatus 10 (e.g., through the pumping chamber 14)to the tissue chamber 30. The port 34 is configured to permit fluid(e.g., perfusate) to be introduced to the tissue chamber 30. In thismanner, fluid can be introduced into the tissue chamber 30 as desired byan operator of the apparatus. For example, in some embodiments, adesired amount of perfusate is introduced into the tissue chamber 30 viathe port 34, such as before disposing the tissue T in the tissue chamber30 and/or while the tissue T is received in the tissue chamber. In someembodiments, the port 34 is a unidirectional port, and thus isconfigured to prevent the flow of fluid from the tissue chamber 30 to anarea external to the tissue chamber through the port. In someembodiments, the port 34 includes a luer lock. The tissue chamber 30 maybe of any suitable volume necessary for receiving the tissue T and arequisite amount of fluid for maintaining viability of the tissue T. Inone embodiment, for example, the volume of the tissue chamber 30 isapproximately 2 liters.

The tissue chamber 30 is formed by a canister 32 and a bottom portion 19of the pumping chamber 14. In a similar manner as described above withrespect to the membrane 20, an upper portion of the tissue chamber(defined by the bottom portion 19 of the pumping chamber 14) can beinclined from the first side 22 towards the second side 24 of theapparatus. In this manner, as described in more detail below, a risingfluid in the tissue chamber 30 will be directed by the inclined upperportion of the tissue chamber towards a valve 36 disposed at a highestportion of the tissue chamber. The valve 36 is configured to permit afluid to flow from the tissue chamber 30 to the pumping chamber 14. Thevalve 36 is configured to prevent flow of a fluid from the pumpingchamber 14 to the tissue chamber. The valve 36 can be any suitable valvefor permitting unidirectional flow of the fluid, including, for example,a ball check valve.

The canister 32 can be constructed of any suitable material. In someembodiments, the canister 32 is constructed of a material that permitsan operator of the apparatus 10 to view at least one of the tissue T orthe perfusate received in the tissue chamber 30. For example, in someembodiments, the canister 32 is substantially transparent. In anotherexample, in some embodiments, the canister 32 is substantiallytranslucent. The tissue chamber 30 can be of any suitable shape and/orsize. For example, in some embodiments, the tissue chamber 30 can have aperimeter that is substantially oblong, oval, round, square,rectangular, cylindrical, or another suitable shape.

In use, the tissue T is coupled to the adapter 26. The pumping chamber14 is coupled to the canister 32 such that the tissue T is received inthe tissue chamber 30. In some embodiments, the pumping chamber 14 andthe canister 32 are coupled such that the tissue chamber 30 ishermetically sealed. A desired amount of perfusate is introduced intothe tissue chamber 30 via the port 34. The tissue chamber 30 can befilled with the perfusate such that the perfusate volume rises to thehighest portion of the tissue chamber. The tissue chamber 30 can befilled with an additional amount of perfusate such that the perfusateflows from the tissue chamber 30 through the valve 36 into the secondportion 18 of the pumping chamber 14. The tissue chamber 30 can continueto be filled with additional perfusate until all atmospheric gas thatinitially filled the second portion 18 of the pumping chamber 14 risesalong the inclined membrane 20 and escapes through the port 38. Becausethe gas will be expelled from the pumping chamber 14 via the port 38before any excess perfusate is expelled (due to gas being lighter, andthus more easily expelled, than liquid), an operator of the apparatus 10can determine that substantially all excess gas has been expelled fromthe pumping chamber when excess perfusate is released via the port. Assuch, the apparatus 10 can be characterized as self-purging. Whenperfusate begins to flow out of the port 38, the apparatus 10 is in a“purged” state (i.e., all atmospheric gas initially within the tissuechamber 30 and the second portion 18 of the pumping chamber 14 has beenreplaced by perfusate). When the purged state is reached, the operatorcan close both ports 34 and 38, preparing the apparatus 10 foroperation.

Oxygen (or another suitable fluid, e.g., gas) is introduced into thefirst portion 16 of the pumping chamber 14 via the valve 12. A positivepressure generated by the introduction of oxygen into the pumpingchamber 14 causes the oxygen to be diffused through the semi-permeablemembrane 20 into the second portion 18 of the pumping chamber. Becauseoxygen is a gas, the oxygen expands to substantially fill the firstportion 16 of the pumping chamber 14. As such, substantially the entiresurface area of the membrane 20 between the first portion 16 and thesecond portion 18 of the pumping chamber 14 is used to diffuse theoxygen. The oxygen is diffused through the membrane 20 into theperfusate received in the second portion 18 of the pumping chamber 14,thereby oxygenating the perfusate.

In the presence of the positive pressure, the oxygenated perfusate ismoved from the second portion 18 of the pumping chamber 14 into thetissue T via the adapter 26. For example, the positive pressure cancause the perfusate to move from the pumping chamber 14 through thelumen of the adapter 26 into the vessel of the tissue T. The positivepressure is also configured to help move the perfusate through thetissue T such that the tissue T is perfused with oxygenated perfusate.

After the perfusate is perfused through the tissue T, the perfusate isreceived in the tissue chamber 30. In this manner, the perfusate thathas been perfused through the tissue T is combined with perfusatepreviously disposed in the tissue chamber 30. In some embodiments, thevolume of perfusate received from the tissue T following perfusioncombined with the volume of perfusate previously disposed in the tissuechamber 30 exceeds a volume (e.g., a maximum fluid capacity) of thetissue chamber 30. A portion of the tissue chamber 30 is flexible andexpands to accept this excess volume. The valve 12 can then allow oxygento vent from the first portion 16 of the pumping chamber 14, thus,reducing the pressure in the pumping chamber 14. As the pressure in thepumping chamber 14 drops, the flexible portion of the tissue chamber 30relaxes, and the excess perfusate is moved through the valve 36 into thepumping chamber 14. The cycle of oxygenating perfusate and perfusing thetissue T with the oxygenated perfusate can be repeated as desired.

An apparatus 100 according to an embodiment is illustrated in FIGS. 2-7.The apparatus 100 is configured to oxygenate a perfusate and to perfusea tissue for extracorporeal preservation of the tissue. The apparatus100 includes a lid assembly 110, a canister 190, and a couplingmechanism 250.

The lid assembly 110 is configured to facilitate transportability of theapparatus. The lid assembly 110 includes a handle 112 and a lid 120. Thehandle 112 is configured to be grasped, e.g., by a hand of a persontransporting the apparatus 100. The handle 112 is coupled to the lid120. The handle 112 can be coupled to the lid 120 using any suitablemechanism for coupling. For example, the handle 112 can be coupled tothe lid 120 with at least one screw (e.g., screw 114 as shown in FIG.2), an adhesive, a hook and loop fastener, mating recesses, or the like,or any combination of the foregoing. An upper portion 122 of the lid 120defines a chamber 124 configured to receive components of a pneumaticsystem 200 and a control system 500, each of which is described in moredetail below. A bottom portion 116 of the handle 112 is configured tosubstantially enclose a top of the chamber 124 defined by the lid 120.

The lid assembly 110 defines a pumping chamber 125 configured to receivea gas, such as oxygen, from the pneumatic system 200, to facilitatediffusion of the oxygen into a perfusate (not shown) and to facilitatemovement of the oxygenated perfusate into a tissue (not shown). Althoughthe apparatus 100 is described herein as being configured for use withoxygen, any suitable gas may be used with apparatus 100 instead of or inaddition to oxygen. A top of the pumping chamber 125 is formed by alower portion 128 of the lid 120. A bottom of the pumping chamber 125 isformed by an upper surface 134 of a base 132 of the lid assembly 110.

As illustrated in an exploded perspective view in FIG. 6, the lidassembly 110 includes a first gasket 142, a membrane 140, and a membraneframe 144. The membrane 144 is disposed within the pumping chamber 125.The first gasket 142 is disposed between the membrane 140 and the lid120 such that the first gasket is engaged with an upper surface 141 ofthe membrane 140 and the lower portion 128 of the lid. The first gasket142 is configured to seal a perimeter of a first portion 127 of thepumping chamber 125 formed between the lower portion 128 of the lid 120and the upper surface 141 of the membrane 140. In other words, the firstgasket 142 is configured to substantially prevent lateral escape of theoxygen from the first portion 127 of the pumping chamber 125 to adifferent portion of the pumping chamber. In the embodiment illustratedin FIG. 6, the first gasket 142 has a perimeter substantially similar inshape to a perimeter defined by the membrane 140 (e.g., when themembrane is disposed on the membrane frame 148). In other embodiments,however, a first gasket can have another suitable shape for sealing afirst portion of a pumping chamber configured to receive oxygen from apneumatic system.

The first gasket 142 can be constructed of any suitable material. Insome embodiments, for example, the first gasket 142 is constructed ofsilicone, an elastomer, or the like. The first gasket 142 can have anysuitable thickness. For example, in some embodiments, the first gasket142 has a thickness within a range of about 0.1 inches to about 0.15inches. More specifically, in some embodiments, the first gasket 142 hasa thickness of about 0.125 inches. The first gasket 142 can have anysuitable level of compression configured to maintain the seal about thefirst portion 142 of the pumping chamber 125 when the components of thelid assembly 110 are assembled. For example, in some embodiments, thefirst gasket 142 is configured to be compressed by about 20 percent. Insome embodiments, the first gasket 142 can provide a leak-proof sealunder operating pressures up to 5 pounds per square inch (psi).

The membrane 140 is configured to permit diffusion of the gas from thefirst portion 127 of the pumping chamber 125 through the membrane to asecond portion 129 of the pumping chamber, and vice versa. The membrane140 is configured to substantially prevent a liquid (e.g., theperfusate) from passing through the membrane. In this manner, themembrane 140 can be characterized as being semi-permeable. A membraneframe 144 is configured to support the membrane 140 (e.g., during theoxygenation and perfusing of the tissue). The membrane frame 144 can bea substantially ring-like structure with an opening at its center. Asshown in FIG. 5, at least a portion of the membrane 140 is disposed(e.g., wrapped) about at least a portion of the membrane frame 144. Insome embodiments, the membrane 140 is stretched when it is disposed onthe membrane frame 144. The membrane 140 is disposed about a lower edgeof the membrane frame 144 such that the membrane 140 is engaged with aseries of protrusions (e.g., protrusion 145 shown in FIG. 5) configuredto help retain the membrane with respect to the membrane frame 144. Atleast a portion of the series of protrusions on the lower edge of themembrane frame 144 are configured to be received in a recess 147 definedby the upper surface 134 of the base 132. As such, the membrane 140 isengaged between the membrane frame 144 and the base 132, whichfacilitates retention of the membrane with respect to the membraneframe. In some embodiments, the first gasket 142 also helps to maintainthe membrane 140 with respect to the membrane frame 144 because thefirst gasket is compressed against the membrane.

As best illustrated in FIG. 4, the membrane 140 is disposed within thepumping chamber 125 at an angle with respect to a horizontal axis A3. Inthis manner, the membrane 140 is configured to facilitate the movementof fluid towards a highest portion of the pumping chamber 125, asdescribed in more detail herein.

The membrane 140 can be of any suitable size. For example, in someembodiments, the upper surface 141 of the membrane 140 can be about 15to about 20 square inches. More specifically, in some embodiments, theupper surface 141 of the membrane 140 can be about 19 square inches. Inanother example, the membrane 140 can have any suitable thickness. Insome embodiments, for example, the membrane 140 is about 0.005 inches toabout 0.010 inches thick. More specifically, in some embodiments, themembrane is about 0.0075 inches thick. The membrane 140 can beconstructed of any suitable material. For example, in some embodiments,the membrane is constructed of silicone, plastic, or another suitablematerial. In some embodiments, the membrane is flexible. As illustratedin FIG. 6, the membrane 140 can be substantially seamless. In thismanner, the membrane 140 is configured to be more resistant to beingtorn or otherwise damaged in the presence of a flexural stress caused bya change pressure in the pumping chamber due to the inflow and/orrelease of oxygen.

The lid 120 includes a purge port 106 disposed at the highest portion ofthe second portion 129 of the pumping chamber 125, as shown in FIG. 4.In some embodiments, the port 106 is disposed at the highest portion ofthe pumping chamber 125 as a whole. In other words, the highest portionof the second portion 129 of the pumping chamber 125 can be the highestportion of the pumping chamber 125. The purge port 106 is configured topermit movement of a fluid from the pumping chamber 125 to an areaexternal to the apparatus 100. The purge port 106 can be similar in manyrespects to a port described herein (e.g., port 38, described above,and/or purge ports 306, 706, described below). The purge port 106 can beany suitable mechanism for permitting movement of the fluid from thepumping chamber 125 into the atmosphere external to the apparatus 100,including, but not limited to, a luer lock fitting. The purge port 106can include a cap (not shown) coupled to the port via a retaining strap.

In some embodiments, the lid 120 is transparent, either in its entiretyor in part (e.g. in the vicinity of the purge port 106). This permits auser to readily view a fluid therein (e.g., any gas bubbles) and toconfirm completion of purging of excess fluid (e.g., the gas bubbles).

Referring to FIG. 4, and as noted above, the upper surface 134 of thebase 132 forms the bottom portion of the pumping chamber 125. The uppersurface 134 of the base 132 is inclined from a first end 102 of theapparatus 100 to a second end 104 of the apparatus. Said another way,the upper surface 134 lies along a plane having an axis different thanthe horizontal axis A3. Because each of the first gasket 142, themembrane 140, and the membrane frame 144 are disposed on the uppersurface 134 of the base 132, each of the first gasket, the membrane, andthe membrane frame are similarly inclined from the first end 102 of theapparatus 100 towards the second end 104 of the apparatus. In thismanner, the base 132 is configured to facilitate movement of a fluidtowards the highest portion of the pumping chamber 125. The angle ofincline of these components may be of any suitable value to allow fluid(e.g., gas bubbles, excess liquid) to flow towards the purge port 106and exit the pumping chamber 125. In some embodiments, the angle ofincline is approximately in the range of 1°-10°, in the range of 2°-6°,in the range of 2.5°-5°, in the range of 4°-5° or any angle of inclinein the range of 1 (e.g., approximately 1°, 2°, 3°, 4°,5°, 6°, 7°, 8°,9°, 10°).

As illustrated in FIG. 4, a valve 138 is disposed at approximately thehighest portion of the lower surface 136 of the base 132. The valve 138is moveable between an open configuration and a closed configuration. Inits open configuration, the valve 138 is configured to permit movementof a fluid from a tissue chamber 192, which is defined by the canister190 and a lower surface 136 of the lid assembly 110, to the pumpingchamber 125 via the valve. Specifically, the valve 138 is configured topermit fluid to move from the tissue chamber 192 into the second portion129 of the pumping chamber 114. In this manner, an excess amount offluid within the tissue chamber 192 can overflow through the valve 138and into the pumping chamber 125. In its closed configuration, the valve138 is configured to substantially prevent movement of a fluid from thepumping chamber 125 to the tissue chamber 192 via the valve. The valve138 is moved from its closed configuration to its open configurationwhen a pressure in the tissue chamber 192 is greater than a pressure inthe pumping chamber 125. In some embodiments, the valve 138 is movedfrom its open position to its closed position when a pressure in thepumping chamber 125 is greater than a pressure in the tissue chamber192. The valve 138 can be biased towards its closed configuration. Insome embodiments, one or more additional valves (not shown) are disposedat other locations of the base 132. In some embodiments, an additionalvalve (not shown) is located at approximately the lowest portion of thelower surface 136 of the base 132.

As illustrated in FIGS. 4 and 6, in some embodiments, the valve 138 is aball check valve. In its closed configuration, a spherical ball of thevalve 138 is disposed on a seat of the valve. In its open configuration,the ball is lifted off of the seat of the valve 138. The ball of thevalve 138 has a near neutral buoyancy. As such, the ball of the valve138 will neither sink nor rise merely because it is in the presence of afluid (e.g., the perfusate, oxygen, or another fluid). The ball of thevalve 138 is configured to rise off of the seat of the valve when thepressure in the tissue chamber 192 is greater than the pressure in thepumping chamber 125. In some embodiments, a protrusion 151 of the lid120 is extended downwardly over the valve 138 to prevent the ball fromrising too high above the seat such that the ball could be laterallydisplaced with respect to the seat. In some embodiments, the ball of thevalve 138 is configured to return to the seat of the valve when thepressure in the pumping chamber is greater than the pressure in thetissue chamber. In some embodiments, the ball of the valve 138 is biasedtowards the seat of the valve by a spring (not shown) extended from thelid 120. The seat of the valve 138 can be conically tapered to guide theball into the seat and to facilitate formation of a positive seal whenstopping flow of fluid from the pumping chamber 125 to the tissuechamber 192.

The base 132 is coupled to the lid 120. In some embodiments, a rim 139of the base 132 and a rim 121 of the lid 120 are coupled together, e.g.,about a perimeter of the pumping chamber 125. The base 132 and the lid120 can be coupled using any suitable mechanism for coupling including,but not limited to, a plurality of screws, an adhesive, a glue, a weld,another suitable coupling mechanism, or any combination of theforegoing. A gasket 148 is disposed between the base 132 and the lid120. The gasket 148 is configured to seal an engagement of the base 132and the lid 120 to substantially prevent fluid in the pumping chamber125 from leaking therebetween. In some embodiments, the gasket 148 is anO-ring.

The base 132 defines a lumen 135 configured to be in fluid communicationwith a lumen 174 of an tissue adapter 170, described in more detailbelow. The base 132 is configured to permit oxygenated perfusate to movefrom the pumping chamber 125 through its lumen 135 into the lumen 174 ofthe tissue adapter 170 towards the tissue chamber 192. In this manner,the lumen 135 of the base 132 is configured to help fluidically couplethe pumping chamber 125 and the tissue chamber 192.

The tissue adapter 170 is configured to substantially retain the tissuewith respect to the apparatus 100. The tissue adapter 170 can be similarin many respects to an adapter described herein (e.g., adapter 26,described above, and/or adapter 770, described below). The tissueadapter 170 includes a handle portion 178, an upper portion 172, and aprotrusion 180, and defines the lumen 174 extended therethrough. Theupper portion 172 of the tissue adapter 170 is extended from a firstside of the handle portion 178. The protrusion 180 of the tissue adapter170 is extended from a second side of the handle portion 178 differentthan the first side of the handle portion. At least a portion of theprotrusion 180 is configured to be inserted into the tissue. Morespecifically, at least a portion of the protrusion 180 is configured tobe inserted into a vessel (e.g., an artery, a vein, or the like) of thetissue. In some embodiments, the protrusion 180 is configured to becoupled to the tissue via an intervening structure, such as silastic orother tubing.

As illustrated in FIG. 4, at least a portion of the protrusion 180includes a series of tapered steps such that a distal end 181 of theprotrusion is narrower than a proximal end 183 of the protrusion. Inthis manner, the protrusion 180 is configured to be inserted into arange of vessel sizes. For example, the protrusion 180 can be configuredto be received in a bodily vessel having a diameter within the range ofabout 3 millimeters to about 8 millimeters. In this manner, theprotrusion 180 is configured to deliver the fluid (e.g., the oxygenatedperfusate) from the pumping chamber 125 to the vessel of the tissue viathe lumen 174 defined by the tissue adapter 170. The vessel of thetissue can be sutured to the protrusion 180 of the adapter 170.

The tissue adapter 170 includes a first arm 182 having a first endportion 185 and a second arm 184 having a second end portion 187. Thefirst and second arms 182, 184 are configured to facilitate retention ofthe tissue with respect to the tissue adapter 170. A retention mechanism(not shown) is configured to be attached, coupled, or otherwise disposedabout each of the first and second arms 182, 184. The retentionmechanism can be any suitable retention mechanism described above withrespect to the apparatus 10, including, for example, a net, a cage, asling, or the like. A middle portion of the retention mechanism isconfigured to be disposed about at least a portion of the tissue coupledto the protrusion 180 of the adapter 170. End portions of the retentionmechanism are configured to be disposed about each of the first andsecond arms 182, 184 of the tissue adapter 170. The first end portion185 of the first arm 182 and the second end portion 187 of the secondarm 184 are each configured to facilitate retention of the end portionsof the retention mechanism with respect to the first and second arms,respectively. For example, as shown in FIG. 4, each of the first andsecond end portions 185, 187 of the first and second arms 182, 184,respectively, defines a shoulder portion configured to help prevent theend portions of the retention mechanism from being inadvertently removedfrom the first or second arm, respectively.

The upper portion 172 of the tissue adapter 170 is configured to couplethe tissue adapter to the base 132. The upper portion 172 of the tissueadapter is configured to be received by the lumen 135 defined by thebase. The upper portion 172 includes a first projection 176 and a secondprojection (not shown) spaced apart from the first projection. Theprojections 176 of the tissue adapter 170 are configured to be receivedby the lumen 135 of the base 132 in opposing spaces between a firstprotrusion 154 and a second protrusion 156 (shown in FIG. 5) disposedwithin the lumen of the base. Once the upper portion 172 is received inthe lumen 135 of the base 132, the tissue adapter 170 can be rotatedapproximately ninety degrees such that its first projection 176 and itssecond projection sit on a shoulder 155, 157 defined by the protrusions154, 156 of the base, respectively. The tissue adapter 170 can berotated in either a clockwise or a counterclockwise direction to alignits projections with the shoulders of the protrusions of the base 132.Similarly, the tissue adapter 170 can be rotated in either the clockwiseor the counterclockwise direction to unalign its projections with theshoulders of the protrusions of the base 132, such as for decoupling ofthe adapter from the base. Said another way, the tissue adapter 170 canbe configured to be coupled to the base 132 with a bayonet joint. Thehandle portion 178 is configured to facilitate coupling and decouplingof the tissue adapter 170 and the base 132. For example, the handleportion 178 is configured to be grasped by a hand of an operator of theapparatus 100. As shown in FIG. 6, the handle portion 178 issubstantially disc-shaped, and includes a series of recesses configuredto facilitate grasping the handle portion with the operator's hand.

A gasket 188 is disposed about the upper portion 172 of the tissueadapter 170 between the handle portion 178 of the adapter and the base132. The gasket 188 is configured to substantially prevent a fluid fromflowing between the pumping chamber 125 and the tissue chamber 192within a channel formed between an outer surface of the upper portion172 of the tissue adapter 170 and an inner surface of the lumen 135 ofthe base 132. In some embodiments, the gasket 188 is compressed betweenthe tissue adapter 170 and the base 132 when the tissue adapter iscoupled to the base.

In some embodiments, at least a portion of the lid assembly 110 isconfigured to minimize flexure of the portion of the lid assembly, suchas may occur in the presence of a positive pressure (or pulse wave)caused by introduction of oxygen into the pumping chamber 125 and/or ofoxygenated perfusate into the tissue chamber 192. For example, asillustrated in FIG. 6, the upper portion 122 of the lid 120 includes aplurality of ribs 126 configured to minimize flexure of the lid 120 whenoxygen is pumped through the pumping chamber 125. In other words, theplurality of ribs 126 structurally reinforces the lid 120 to helpprevent the lid 120 from flexing. The plurality of ribs 126 are extendedfrom a top surface of the lid 120 in a substantially parallelconfiguration. In another example, the lower portion 128 of the lid 120can include a plurality of ribs (not shown) configured to reinforce thetop of the pumping chamber 125 to help prevent flexure of the top of thepumping chamber 125 during pumping of oxygen through the lid assembly110. In yet another example, the base 132 is configured to substantiallyminimize flexure of the base, such as may occur in the presence of apositive pressure caused by the introduction of oxygen into the pumpingchamber 125 and/or of oxygenated perfusate into the tissue chamber 192.As illustrated in FIG. 6, the base 132 includes a plurality of ribs 131extended from its upper surface 134. As illustrated in FIG. 5, the base132 includes a plurality of ribs 133 extended from its lower surface136. Each of the plurality of ribs 131, 133 is configured to reinforcethe base 132, which helps to minimize flexure of the base.

The lid assembly 110 includes a fill port 108 configured to permitintroduction of a fluid (e.g., the perfusate) into the tissue chamber192 (e.g., when the lid assembly is coupled to the canister 190). Thefill port 108 can be similar in many respects another port describedherein (e.g., port 34, described above, and/or port 708, describedbelow). In the embodiment illustrated in FIG. 4 and FIG. 6, the fillport 108 is formed by a fitting 107 coupled to the lid 120 and thatdefines a lumen 109 in fluidic communication with a lumen 143 in thefirst gasket 142, which lumen 143 is in fluidic communication with alumen 137 defined by the base 132, which lumen 137 is in fluidiccommunication with the tissue chamber 192. The fitting 107 can be anysuitable fitting, including, but not limited to, a luer lock fitting.The fill port 108 can include a cap (not shown) removably coupled to theport via a retaining strap. The cap can help prevent inadvertentmovement of fluid, contaminants, or the like through the fill port 108.

The lid assembly 110 is configured to be coupled to the canister 190.The canister 190 can be similar in many respects to a canister describedherein (e.g., canister 32, described above, and/or canister 390, 790,990, described below). The canister includes a wall 191, a floor 193,and a compartment 194 defined on its sides by the wall and on its bottomby the floor. The compartment 194 can form a substantial portion of thetissue chamber 192. As shown in FIG. 4, at least a portion of the lidassembly 110 (e.g., the base 132) is configured to be received in thecompartment 194 of the canister 190. A gasket 152 is disposed betweenthe base 132 and an inner surface of the wall 191 of the canister 190.The gasket 152 is configured to seal the opening between the base 132and the wall 191 of the canister 190 to substantially prevent flow offluid (e.g., the perfusate) therethrough. The gasket 152 can be anysuitable gasket, including, for example, an O-ring. In some embodiments,the canister 190 includes a port 196 disposed on the wall 191 of thecanister.

The floor 193 of the canister 190 is configured to flex when a firstpressure within the tissue chamber 192 changes to a second pressurewithin the tissue chamber, the second pressure different than the firstpressure. More specifically, in some embodiments, the floor 193 of thecanister 190 is configured to flex when a first pressure within thetissue chamber 192 is increased to a second pressure greater than thefirst pressure. For example, the floor 193 of the canister 190 can beconfigured to flex in the presence of a positive pressure (or a pulsewave) generated by the pumping of the oxygenated perfusate from thepumping chamber 125 into the tissue chamber 192, as described in moredetail below. In some embodiments, the floor 193 of the canister 190 isconstructed of a flexible membrane. The floor 193 of the canister 190can have any suitable thickness. For example, in some embodiments, thefloor 193 of the canister 190 has a thickness of about 0.075 to about0.085 inches. In some embodiments, the floor 193 of the canister 190 isabout 0.080 inches thick.

The canister 190 can be configured to enable an operator of theapparatus 100 to view the tissue when the tissue is sealed within thetissue chamber 192. In some embodiments, for example, at least a portionof the canister 190 (e.g., the wall 191) is constructed of a transparentmaterial. In another example, in some embodiments, at least a portion ofthe canister 190 (e.g., the wall 191) is constructed of a translucentmaterial. In some embodiments, the canister 190 includes a window (notshown) through which at least a portion of the tissue chamber 192 can beviewed.

As noted above, the coupling mechanism 250 is configured to couple thecanister 190 to the lid assembly 110. In the embodiment illustrated inFIGS. 2-4, the coupling mechanism 250 is a substantially C-shaped clamp.The clamp 250 includes a first arm 252 and a second arm 254. The arms252, 254 are configured to be disposed on opposite sides of theapparatus 100 about a lower rim of the lid 120 and an upper rim of thecanister 190. The arms 252, 254 of the clamp 250 are coupled at thefirst side 102 of the apparatus 100 by a hinge 256. The clamp 250 is inan open configuration when the first arm 252 is movable with respect tothe second arm 254 (or vice versa). The arms 252, 254 are configured tobe coupled at a second side 104 of the apparatus 100 by a locking lever258. The clamp 250 is in a closed configuration when its arms 252, 254are coupled at the second side 104 of the apparatus 100 by the lockinglever 258. In some embodiments, the clamp 250 is configured for a singleuse. More specifically, the clamp 250 can be configured such that whenit is moved from its closed configuration to its open configuration, theclamp is prevented from being returned to its closed configuration. Inother words, once an original seal formed by the clamp in its closedconfiguration is broken by opening the clamp, the clamp can no longer beresealed. In use, the clamp 250 being configured for a single use canhelp an operator of the apparatus 100 ensure that tissue being preservedwithin the apparatus is free of tampering. In some embodiments, theclamp 250 remains coupled to one of the canister 190 or the lid 120 whenthe clamp is moved to its open configuration from its closedconfiguration.

Although the coupling mechanism 250 has been illustrated and describedas being a clamp (and a band clamp specifically), in other embodiments,another suitable mechanism for coupling the canister 190 to the lidassembly 110 can be used. For example, the coupling mechanism 250 can bedesigned as a toggle clamp that is attached to the lid assembly 110. Thetoggle clamp can be a toggle action clamp that is manually movablebetween unclamped, center, and over-center (clamped) positions. Anysuitable number of toggle clamps may be employed, such as one, two,three, four or more toggle clamps.

As noted above, the apparatus 100 is configured for controlled deliveryof fluid (e.g., oxygen) from an external source (not shown) into thepumping chamber 125 of the lid assembly 110. The external source can be,for example, an oxygen cylinder. In some embodiments, the pneumaticsystem 200 is configured for controlled venting of fluid (e.g., carbondioxide) from the pumping chamber 125 to an area external to theapparatus 100 (e.g., to the atmosphere). The pneumatic system 200 ismoveable between a first configuration in which the pneumatic system isdelivering fluid to the pumping chamber 125 and a second configurationin which the pneumatic system is venting fluid from the pumping chamber125. The pneumatic system 200 includes a supply line 204, a vent line206, a control line 208, a valve 210, a printed circuit board assembly(“PCBA”) 214, and a power source 218.

The supply line 204 is configured to transmit fluid from the externalsource to the valve 210. A first end of the supply line 204 external tothe lid 120 is configured to be coupled to the external source. A secondend of the supply line 204 is configured to be coupled to the valve 210.Referring to FIGS. 6 and 7, a portion of the supply line 204 between itsfirst end and its second end is configured to be extended from an areaexternal to the lid 120 through an opening 123 defined by the lid intothe chamber 124 defined by the lid. In some embodiments, the supply line204 is configured to transmit fluid to the valve 210 at a pressure ofabout 2 pounds per square inch (“p.s.i.”), plus or minus ten percent.

The vent line 206 is configured to transmit fluid (e.g., oxygen, carbondioxide) from the valve 210 to an area external to the chamber 124 ofthe lid 120. A first end of the vent line 206 is configured to becoupled to the valve 210. In some embodiments, the second end of thevent line 206 is a free end such that the fluid is released into theatmosphere. A portion of the vent line 206 between its first end and itssecond end is configured to be extended from the valve 210 through thechamber 124 and the opening 123 defined by the lid 120 to the areaexternal to the lid.

The control line 208 is configured to transmit fluid between the valve210 and the pumping chamber 125 of the lid assembly 110. A first end ofthe control line 208 is coupled to the valve 210. A second end of thecontrol line 208 is coupled to the pumping chamber 125. In someembodiments, as shown in FIG. 7, the control line 208 is mechanicallyand fluidically coupled to the pumping chamber 125 by an adapter 209.The adapter 209 can be any suitable mechanism for coupling the controlline 208 to the pumping chamber 125. In some embodiments, for example,the adapter 209 includes a male fitting on a first end of the adapterthat is configured to be disposed in the second end of the control line208 and threaded portion on a second end of the adapter configured to bereceived in a correspondingly threaded opening in the lower portion 128of the lid 120. When the pneumatic system 200 is in its firstconfiguration, the control line 208 is configured to transmit fluid fromthe supply line 204 via the valve 210 to the pumping chamber 125. Whenthe pneumatic system 200 is in its second configuration, the controlline 208 is configured to transmit fluid from the pumping chamber 125 tothe vent line 206 via the valve 210. Each of the foregoing lines (i.e.,supply line 204, vent line 206, control line 208) can be constructed ofany suitable material including, for example, polyurethane tubing.

The valve 210 is configured to control the flow of oxygen into and outof the pumping chamber 125. In the embodiment illustrated in FIG. 7, thevalve 210 is in fluidic communication with each of the supply line 204,the vent line 206, and the control line 208 via a first port, a secondport, and a third port (none of which are shown in FIG. 7),respectively. In this manner, the valve 210 is configured to receive thefluid from the supply line 204 via the first port. In some embodiments,the first port defines an orifice that is about 0.10 to about 0.60 mm insize. In other embodiments, the first port defines an orifice that isabout 0.15 to about 0.50 mm in size, about 0.20 to about 0.40 mm insize, about 0.20 to about 0.30 mm in size, or about 0.25 to about 0.30mm in size. Specifically, in some embodiments, the first port defines anorifice that is about 0.25 mm in size. The valve 210 is configured todeliver the fluid to the vent line 206 via the second port.Additionally, the valve 210 is configured to receive the fluid from anddeliver the fluid to the control line 208 via the third port.Specifically, the valve 210 is movable between a first configuration anda second configuration. In its first configuration, the valve 210 isconfigured to permit the flow of fluid from the supply line 204 throughthe valve 210 to the control line 208. As such, when the valve 210 is inits first configuration, the pneumatic system 200 is in its firstconfiguration. In its second configuration, the valve 210 is configuredto permit the flow of fluid from the control line 208 through the valveto the vent line 206. As such, when the valve 210 is in its secondconfiguration, the pneumatic system 200 is in its second configuration.

The valve 210 is in electrical communication with the power source 218.In some embodiments, for example, the valve 210 is in electricalcommunication with the power source 218 via the PCBA 214. In theembodiment illustrated in FIGS. 6 and 7, the PCBA 214 is disposed in thechamber 124 between the valve 210 and the power source 218. In someembodiments, the PCBA 214 includes an electrical circuit (not shown)configured to electrically couple the power source 218 to the valve 210.The power source 218 is configured to provide power to the valve 210 toenable the valve 210 to control the flow of oxygen. In some embodiments,the power source 218 is configured to provide power to the valve 210 toenable the valve to move between its first configuration and its secondconfiguration. The power source can be any suitable source of powerincluding, for example, a battery. More specifically, in someembodiments, the power source is a lithium battery (e.g., a Li/MnO₂ 2/3Abattery). In another example, the power source can be an AA, C or D cellbattery.

The valve 210 can be any suitable mechanism for controlling movement ofthe fluid between the first port, the second port, and the third port(and thus the supply line 204, vent line 206, and the control line 208,respectively). For example, in the embodiment illustrated in FIG. 7, thevalve 210 is a solenoid valve. As such, in operation, the valve 210 isconfigured to convert an electrical energy received from the powersource 218 to a mechanical energy for controlling the flow of oxygentherein. In some embodiments, for example, the valve 210 is configuredto move to its first configuration when power is received by the valvefrom the power source 218. In some embodiments, the valve 210 isconfigured to move to its second configuration when the valve iselectrically isolated (i.e., no longer receiving power) from the powersource 218. In other words, the valve 210 is configured to deliver fluid(e.g., oxygen) to the pumping chamber 125 when the solenoid of the valveis energized by the power source 218, and the valve is configured tovent fluid (e.g., oxygen, carbon dioxide) from the pumping chamber whenthe solenoid of the valve is not energized by the power source. In someembodiments, the valve 210 is biased towards its second (or venting)configuration (in which power is not being provided from the powersource 218 to the valve). Because the power source 218 is configured tonot be in use when the pneumatic system 200 is not delivering oxygen tothe pumping chamber 125, the usable life of the power source isextended, which enables the tissue to be extracorporeally preservedwithin the apparatus 100 for a longer period of time. For example, insome embodiments, the solenoid of the valve 210 is configured to receivepower from the power source 218 for about 20 percent of the total timethe apparatus 100, or at least the pneumatic system 200 of theapparatus, is in use.

In some embodiments, the flow of fluid from the supply line 204 to thevalve 210 is substantially prevented when the valve is in its secondconfiguration. In this manner, the flow of oxygen into the valve 210from the supply line 204 is stopped while the valve is venting fluidfrom the pumping chamber 125. As such, the overall oxygen use of theapparatus 100 is reduced. In other embodiments, when the valve 210 is inits second configuration, the fluid being transmitted into the valvefrom the supply line 204 is transmitted through the valve to the ventline 206 without entering the pumping chamber 125. In this manner, theinflow of fluid from the supply line 204 to the valve 210 issubstantially continuous. Accordingly, the flow of fluid from the valve210 to the vent line 206 is also substantially continuous because thevalve 210 is substantially continuously venting fluid from at least oneof the supply line 204 and/or the control line 208.

Referring to a schematic illustration of the pneumatic system andpumping chamber in FIG. 8, the pneumatic system 200 is configured tocontrol a change in pressure within the pumping chamber 125 of the lidassembly 110. In some embodiments, the pneumatic system 200 isconfigured to control the pressure within the pumping chamber 125 viathe control line 208. More specifically, the rate of flow of fluidbetween the valve 210 and the pumping chamber 125 via the control line208 is determined by a control orifice 207 disposed within the controlline. The control orifice 207 can be, for example, a needle valvedisposed within the control line 208. In some embodiments, the controlorifice is about 0.10 to about 0.60 mm in size. In other embodiments,the first port defines an orifice that is about 0.15 to about 0.50 mm insize, about 0.20 to about 0.40 mm in size, about 0.20 to about 0.30 mmin size, or about 0.25 to about 0.30 mm in size. For example, in someembodiments, the control orifice 207 is about 0.25 mm in size. Becausethe rate of a change (e.g., rise, fall) in pressure within the pumpingchamber 125 is based on the rate of flow of the fluid between the valve210 and the pumping chamber 125 via the control line 208, the pressurewithin the pumping chamber 125 is also determined by the size of thecontrol orifice 207 in the control line 208.

The pneumatic system 200 can be configured to move between its firstconfiguration and its second configuration based on a predeterminedcontrol scheme. In some embodiments, the pneumatic system 200 isconfigured to move between its first configuration and its secondconfiguration on a time-based control scheme. In some embodiments, thepneumatic system 200 is configured to move from its first configurationto its second configuration after a first period of time has elapsed.For example, the pneumatic system 200 can be configured to move from itsfirst configuration to its second configuration after about 170milliseconds. As such, the pneumatic system 200 is configured to deliverfluid (e.g., oxygen) to the pumping chamber 125 for the first timeperiod (e.g., about 170 milliseconds). The pneumatic system 200 isconfigured to move from its second configuration to its firstconfiguration after a second period of time has elapsed. For example,the pneumatic system 200 can be configured to move from its secondconfiguration to its first configuration after being in its secondconfiguration for about 700 milliseconds. As such, the pneumatic system200 is configured to vent fluid (e.g. carbon dioxide) from the pumpingchamber 125 for the second time period (e.g., about 700 milliseconds).The pneumatic system 200 is configured to alternate between its firstconfiguration and its second configuration, and thus between deliveringfluid into the pumping chamber 125 and venting fluid from the pumpingchamber.

Although the pneumatic system 200 has been illustrated and describedabove as having a time-based control scheme, in some embodiments, thepneumatic system 200 is configured to move between its firstconfiguration and its second configuration on a pressure-based controlscheme. In some embodiments, the pneumatic system 200 is configured tomove from its first configuration to its second configuration when apressure within the pumping chamber 125 reaches a first thresholdpressure. For example, the pneumatic system 200 can be configured tomove from its first configuration to its second configuration when thepressure within the pumping chamber 125 is about 20 mmHg (millimeters ofmercury), about 25 mmHg, about 30 mmHg, about 35 mmHg, about 40 mmHg,about 45 mmHg or about 50 mmHg. The pneumatic system 200 can beconfigured to move from its second configuration to its firstconfiguration when a pressure within the pumping chamber 125 reaches asecond threshold pressure. For example, the pneumatic system 200 can beconfigured to move from its second configuration to its firstconfiguration when the pressure within the pumping chamber 125 is about0 mmHg, about 5 mmHg, about 10 mmHg or about 15 mmHg. Said another way,when the pressure within the pumping chamber 125 is increased from thesecond threshold pressure to the first threshold pressure, the valve 210is switched from delivering fluid to the pumping chamber to ventingfluid from the pumping chamber. Similarly, when the pressure within thepumping chamber 125 is decreased from the first threshold pressure tothe second threshold pressure, the valve 210 is switched from ventingfluid from the pumping chamber to delivering fluid to the pumpingchamber.

Because the pneumatic system 200 is configured to alternate between itsfirst configuration and its second configuration, the pneumatic system200 can be characterized as being configured to deliver oxygen to thepumping chamber 125 via a series of intermittent pulses. In someembodiments, however, the pneumatic system 200 is configured to deliveroxygen to the pumping chamber 125 in a substantially constant flow. Instill another example, the pneumatic system 200 can be configured toselectively deliver oxygen in each of a substantially constant flow anda series of intermittent pulses. In some embodiments, the pneumaticsystem 200 is configured to control the flow of fluid within the pumpingchamber 125, including the delivery of oxygen to the pumping chamber, inany combination of the foregoing control schemes, as desired by anoperator of the apparatus 100.

Although the pneumatic system 200 has been illustrated and describedherein as controlling the change in pressure within the pumping chamber125 via a control orifice disposed in the control line 208, in otherembodiments, a pneumatic system is configured to control the pressurewithin the pumping chamber via at least one control orifice disposedwithin at least one of the supply line and the vent line. Retelling toFIG. 9, in some embodiments of a pneumatic system 220, a larger controlorifice 223 is disposed within the supply line 222. In this manner, thepneumatic system 220 can permit a larger and/or quicker inflow of fluidfrom the supply line 222 to the pumping chamber, and thus can cause aquick pressure rise within the pumping chamber 228. In another example,in some embodiments, a smaller control orifice 225 is disposed withinthe vent line 224. In this manner, the pneumatic system 220 can restrictthe flow of fluid venting through the vent line 224 from the pumpingchamber 228, and thus can cause a slower or more gradual decline inpressure within the pumping chamber. As compared to pneumatic system200, pneumatic system 220 can permit a shorter time period when thevalve 210 is energized, thereby allowing power source 218 to operate theapparatus for a longer period.

In use, the tissue is coupled to the tissue adapter 170. The lidassembly 110 is disposed on the canister 190 such that the tissue isreceived in the tissue chamber 192. The lid assembly 110 is coupled tothe canister 190. Optionally, the lid assembly 110 and the canister 190are coupled via the clamp 250. A desired amount of perfusate isdelivered to the tissue chamber 192 via the fill port 108. Optionally, adesired amount of perfusate can be disposed within the compartment 194of the canister 190 prior to disposing the lid assembly 110 on thecanister. In some embodiments, a volume of perfusate greater than avolume of the tissue chamber 192 is delivered to the tissue chamber suchthat the perfusate will move through the ball check valve 138 into thesecond portion 129 of the pumping chamber 125.

A desired control scheme of the pneumatic system 200 is selected. Oxygenis introduced into the first portion 127 of the pumping chamber 125 viathe pneumatic system 200 based on the selected control scheme. Thepneumatic system 200 is configured to generate a positive pressure bythe introduction of oxygen into the first portion 127 of the pumpingchamber 125. The positive pressure helps to facilitate diffusion of theoxygen through the membrane 140. The oxygen is diffused through themembrane 140 into the perfusate disposed in the second portion 129 ofthe pumping chamber 125, thereby oxygenating the perfusate. Because theoxygen will expand to fill the first portion 127 of the pumping chamber125, substantially all of an upper surface 141 of the membrane 140 whichfaces the first portion of the pumping chamber can be used to diffusethe oxygen from the first portion into the second portion 129 of thepumping chamber.

As the tissue uses the oxygen, the tissue will release carbon dioxideinto the perfusate. In some embodiments, the carbon dioxide is displacedfrom the perfusate, such as when the pneumatic system 200 the oxygen isdiffused into the perfusate because of the positive pressure generatedby the pneumatic system. Such carbon dioxide can be diffused from thesecond portion 129 of the pumping chamber 125 into the first portion 127of the pumping chamber 125. Carbon dioxide within the first portion 127of the pumping chamber is vented via the control line 208 to the valve210, and from the valve through the vent line 206 to the atmosphereexternal to the apparatus 100.

The positive pressure also causes the membrane 140 to flex, whichtransfers the positive pressure in the form of a pulse wave into theoxygenated perfusate. The pulse wave generated by the pumping chamber isconfigured to facilitate movement of the oxygenated perfusate from thesecond portion 129 of the pumping chamber 125 into the tissue via thetissue adapter 170, thus perfusing the tissue. In some embodiments, thepumping chamber 125 is configured to generate a pulse wave that is anabout 60 Hz pulse. In some embodiments, the pumping chamber 125 isconfigured to generate a pulse wave through the perfusate that isconfigured to cause a differential pressure within the tissue chamber192 to be within the range of about 0 mmHg to about 50.0 mmHg. Morespecifically, in some embodiments, the pumping chamber 125 is configuredto generate a pulse wave through the perfusate that is configured tocause a differential pressure within the tissue chamber 192 to be withinthe range of about 5 mmHg to about 30.0 mmHg.

At least a portion of the perfusate perfused through the tissue isreceived in the tissue chamber 192. In some embodiments, the pulse waveis configured to flow through the perfusate disposed in the tissuechamber 192 towards the floor 193 of the canister 190. The floor 193 ofthe canister 190 is configured to flex when engaged by the pulse wave.The floor 193 of the canister 190 is configured to return the pulse wavethrough the perfusate towards the top of the tissue chamber 192 as thefloor 193 of the canister 190 is returned towards its originalnon-flexed position. In some embodiments, the returned pulse wave isconfigured to generate a sufficient pressure to open the ball checkvalve 138 disposed at the highest position in the tissue chamber 192. Inthis manner, the returned pulse wave helps to move the valve 138 to itsopen configuration such that excess fluid (e.g., carbon dioxide releasedfrom the tissue and/or the perfusate) can move through the valve fromthe tissue chamber 192 to the pumping chamber 125.

The foregoing perfusion cycle can be repeated as desired. For example,in some embodiments, the pneumatic system 200 is configured to begin aperfusion cycle approximately every second based on a time-based controlscheme. As such, the pneumatic system 200 is configured to power on todeliver oxygen to the pumping chamber 125 for several milliseconds. Thepneumatic system 200 can be configured to power off for severalmilliseconds, for example, until time has arrived to deliver asubsequent pulse of oxygen to the pumping chamber 125. Because thepneumatic system 200, and the solenoid valve 210 specifically, is onlypowered on when needed to transmit a pulse of oxygen to the pumpingchamber, the usable life of the power source 218 can be extended for alonger period of time.

An apparatus 300 according to an embodiment is illustrated in FIGS.10-16. The apparatus 300 is configured to oxygenate a perfusate and toperfuse a tissue for extracorporeal preservation of the tissue. Theapparatus 300 includes a lid assembly 310, a canister 390, and acoupling mechanism 450. Unless stated otherwise, apparatus 300 can besimilar in many respects (e.g., form and/or function) to the apparatusdescribed herein (e.g., apparatus 10, 100, 700 (described below)), andcan include components similar in many respects (e.g., form and/orfunction) to components of such apparatus. For example, the canister 390can be similar to the canister 190.

The lid assembly 310 includes a lid cover 314 (e.g., as shown in FIG.10) and a lid 320 (e.g., as shown in FIG. 12). The lid cover 314 iscoupled to the lid 320. The lid cover 314 can be coupled to the lid 320using any suitable mechanism for coupling. For example, the lid cover314 can be coupled to the lid 320 with at least one of a screw, anadhesive, a hook and loop fastener, mating recesses, or the like, or anycombination of the foregoing. A chamber 324 is formed between an upperportion 322 of the lid 320 and a bottom portion 316 of the lid cover314. The chamber 324 is configured to receive components of a pneumaticsystem (e.g., the pneumatic system 200 described above) and the controlsystem 500 (described in detail below with respect to FIG. 17).

The lid assembly 310 includes a first gasket 342, a membrane 340, and amembrane frame 344 disposed on the upper portion 322 of the lid 320. Thelid assembly 310 defines a pumping chamber 325 configured to receiveoxygen from the pneumatic system 200, to facilitate diffusion of theoxygen into a perfusate (not shown) and to facilitate movement of theoxygenated perfusate into a tissue (not shown). A top of the pumpingchamber 325 is formed by the membrane frame 344. A bottom of the pumpingchamber 325 is formed by an upper surface 334 of a base 332 of the lidassembly 310.

One or more components of the lid assembly 310 (e.g., the lid 320 and/orthe lid cover 314) can be transparent, either in its entirety or inpart. Retelling to FIGS. 10 and 12, the lid cover 314 includes a window(not shown), and the lid 320 includes a transparent portion 326 adjacentto, or at least in proximity to, a purge port 306. The transparentportion 326 permits a user to view any excess fluid (e.g., in the formof gas bubbles) in the pumping chamber 325 and to confirm when theexcess fluid has been purged from the pumping chamber 325.

The first gasket 342 is disposed between the membrane 340 and themembrane frame 344 such that the first gasket is engaged with an uppersurface 341 of the membrane 340. The first gasket 342 is configured toseal a perimeter of a first portion 327 of the pumping chamber 325formed between the membrane frame 344 and the upper surface 341 of themembrane 340. In other words, the first gasket 342 is configured tosubstantially prevent lateral escape of oxygen from the first portion327 of the pumping chamber 325 to a different portion of the pumpingchamber. The first gasket 342 has a perimeter substantially similar inshape to a perimeter defined by the membrane 340 (e.g., when themembrane is disposed on the membrane frame 344). In other embodiments,however, a gasket can have another suitable shape for sealing the firstportion 327 of the pumping chamber 325.

The membrane 340 is configured to permit diffusion of gas (e.g., oxygen,carbon dioxide, etc.) from the first portion 327 of the pumping chamber325 through the membrane to a second portion 329 of the pumping chamber,and vice versa. The membrane 340 is configured to substantially preventa liquid (e.g., the perfusate) from passing through the membrane. Inthis manner, the membrane 340 can be characterized as beingsemi-permeable. The membrane frame 344 is configured to support themembrane 340 (e.g., during the oxygenation and perfusion of the tissue).At least a portion of the membrane 340 is disposed (e.g., wrapped) aboutat least a portion of the membrane frame 344. In some embodiments, themembrane 340 is stretched when it is disposed on the membrane frame 344.The membrane 340 is disposed about a bottom rim of the membrane frame344 such that the membrane 340 is engaged with a series of protrusions(e.g., the protrusions 345 shown in FIG. 12) configured to help retainthe membrane 340 with respect to the membrane frame 344. The lid 320 andthe membrane frame 344 are designed for oblique compression of the firstgasket 342 therebetween. The lid 320 is designed such that the membrane340, when stretched and disposed on the membrane frame 344, is virtuallycoplanar with a bottom portion 328 of the lid 320, which is inclinedfrom a first side of the apparatus 300 towards a second side of theapparatus 300 (i.e., towards the purge port 306). As such, excess fluid(e.g., gas bubbles, perfusate, etc.) is more effectively purged from thepumping chamber 325, e.g., to prevent gas bubbles or the like from beingtrapped therein.

The pumping chamber 325 includes an obstruction free second portion 329.The second portion 329 of the pumping chamber 325 is configured toreceive fluid (e.g., the perfusate) from the canister 390, as describedin more detail below. The second portion 329 of the pumping chamber 325is configured to contain the fluid for oxygenation of the fluid asoxygen is pumped into the first portion 327 of the pumping chamber 325and permeated through the membrane 340 into the second portion 329 ofthe pumping chamber, thereby facilitating oxygenation of the fluidcontained therein. In some embodiments, the lid 320 includes one or morepurging structures, such as a lumen (not shown), configured to helpavoid trapping of gas bubbles and/or other fluid at the membrane-lidinterface.

Referring to FIG. 14, the base 332 includes return flow valves 338A,338B. Each return flow valve 338A, 338B is configured to permit fluid toflow from the canister 390 into the pumping chamber 325. The valves338A, 338B each can be any suitable type of valve, including, forexample, a ball check valve. Each valve 338A, 338B can include a returnjet 360A, 360B, respectively, configured to focus fluid flowing from thecanister 390 into the pumping chamber 325 onto the membrane 340. Becausethe membrane 340 is inclined towards the purge port 306, the focusedflow of fluid from the return jets 360A, 360B onto the membrane 340 canhelp facilitate movement of the fluid towards the purge port 306,thereby facilitating purging of excess fluid from the apparatus 300.Although illustrated as being nozzle-shaped, other designs of the jets360A, 360B are suitable. The jets 360A, 360B are also configured toenhance mixing of fluid (e.g., perfusate) within the pumping chamber325, which facilitates oxygenation of the fluid returning into thepumping chamber 325 from the canister 390.

Although lid 320 and the membrane frame 344 are illustrated (e.g., inFIG. 16A) and described as being configured to obliquely compress thefirst gasket 342 therebetween, in some embodiments, an apparatus caninclude a lid and membrane frame configured to differently compress agasket therebetween. For example, retelling to FIG. 16B, a lid 420 and amembrane frame 444 are configured to axially compress a first gasket442. In some embodiments, one or more additional purging structures canbe twined on a bottom portion 428 of the lid 420, such as a lumen (notshown), to prevent the trapping of gas bubbles and/or other fluid at themembrane-lid interface.

The coupling mechanism 450 is configured to couple the lid assembly 310to the canister 390. The coupling mechanism 450 can include a firstclamp 312 and a second clamp 313 different than the first clamp. Thefirst clamp 312 and the second clamp 313 can be disposed on opposingsides of the lid assembly 310. Each of the clamps 312, 313 areconfigured to be disposed about a portion of a lower rim of the lid 320and an upper rim of the canister 390. The clamps 312, 313 are configuredto be moved between a first, or open configuration in which the lidassembly 310 and the canister 390 are freely removable from each other,and a second, or closed, configuration in which the lid assembly 310 andthe canister 390 are not freely removably from each other. In otherwords, in its second configuration, the handles 312, 313 of the couplingmechanism 450 are configured to lock the lid assembly 310 to thecanister 390. The clamps 312, 313 can be any suitable clamp, including,for example, a toggle clamp.

Referring to FIG. 17, the control system 500 includes a processor 502, atissue chamber pressure sensor 506, a pumping chamber pressure sensor510, a solenoid 514, a display unit 518, and a power source 520. In someembodiments, the control system 500 includes additional components, suchas, for example, components configured for wired or wireless networkconnectivity (not shown) for the processor 502.

The control system 500 is described herein with reference to theapparatus 300, however, the control system is suitable for use withother embodiments described herein (e.g., apparatus 10, 100, and/or700). The pumping chamber pressure sensor 510 is configured to detectthe oxygen pressure in the pumping chamber 325. Because the pumpingchamber 325 is split into the first and second portions 327, 329,respectively, by the semi-permeable membrane 340, which is configured toundergo relatively small deflections, the oxygen pressure in the firstportion 327 of the pumping chamber 325 is approximately equal to thefluid (e.g., perfusate) pressure in the second portion 329 of thepumping chamber 325. Therefore, measuring the fluid pressure in eitherthe first portion 327 or the second portion 329 of the pumping chamber325 approximates the fluid pressure in the other of the first portion orthe second portion of the pumping chamber 325.

The tissue chamber pressure sensor 506 is configured to detect the fluidpressure in the canister 390. Each pressure sensor 506, 510 can beconfigured to detect the fluid pressure in real-time and permitinstantaneous determination of small pressure changes. Examples ofpressure sensors that can be used include, but are not limited to,analog pressure sensors available from Freescale (e.g., MPXV5010GP-NDD)and from Honeywell (e.g., HSC-MRNNOO1PGAA5). At least one of thepressure sensors 506, 510 can be configured to measure pressures between0-1.0 psig with a 5 volt power supply. In some embodiments, at least oneof the pressure sensors 506, 510 can be configured to detect pressurevariations as small as 0.06 mmHg. The sensors 506, 510 can be placed inthe chamber 324 at the same height to avoid pressure head measurementerrors.

The solenoid 514 is disposed in the chamber 324. The solenoid 514 isconfigured to control the opening and/or closing of one or more valves(not shown in FIG. 17) for gas flow to and from the pumping chamber 325.The solenoid 514 is operably connected to the power source 520 foroptimal power management.

The display unit 518 is configured to display one or more parameters.Display parameters of the display unit 518 can include, for example,elapsed time of operation, operating temperature, flow rate, and/orresistance, which are key metrics for determining the overall health ofthe tissue being transported by the apparatus 300. Calculation of theflow rate and resistance parameters is described in more detail below.The processor 502 is configured to receive information associated withthe pressure in the pumping chamber 325 and in the canister 390 via thesensors 510, 506, respectively. The processor 502 is configured tocontrol operation of the solenoid 514, to control the supply of powerfrom the power source 520 to the solenoid 514, and to display operatingparameters on the display unit 518.

The processor 502 is configured to calculate the flow rate andresistance, as illustrated in FIG. 18. Flow rate is a measure of thetissue's compliance to fluid flow around the tissue (e.g. blood flow),and can be a significant indicator of tissue viability. In someembodiments, the processor 502 is configured to evaluate such parameters(i.e., flow rate and resistance) continually and in real time. In someembodiments, the processor 502 is configured to periodically evaluatesuch parameters at predetermined time intervals.

Referring to FIG. 18, a flow chart of a method 600 for evaluating aparameter, such as flow rate resistance, according to an embodiment isillustrated. The method 600 is described herein with respect toapparatus 300 and control unit 500, however, can be performed by anotherapparatus described herein. At 602, the number of beats/minute (bpm) isdetermined As used herein, “beat” refers to a pressure increase causedby a first volume of fluid (e.g., oxygen from pneumatic system 200)being introduced (e.g., intermittently) into the pumping chamber 325,which in turn causes a pressure wave that in turn causes a second volumeof fluid (e.g., oxygenated perfusate) to be pumped or otherwisetransferred from the pumping chamber 325 towards the canister 390 and/ora tissue contained in the canister 390. Determination of the bpm can bebased on the frequency with which the solenoid 514 (under the control ofprocessor 502) permits gas exchange via the control orifice.

Because the canister 390 is compliant (i.e., it has a flexible floor393), the canister flexes with each “beat” and then returns to itsstarting position. As the canister 390 floor flexes, the canisteraccepts the second volume of fluid from the pumping chamber 325. Whenthe floor 393 of the canister 390 relaxes, the second volume of fluidreturns to the pumping chamber 325 through the valves 338A, 338B. Thecanister 390 floor 393 flexing and relaxing process can be repeated foreach beat.

As the second volume of fluid enters the canister 390, pressure in thecanister 390 (or more specifically, a tissue chamber 392, illustrated inFIG. 14, defined by the canister 390 and the lid assembly 310) rises andcauses the canister 390 floor 393 to flex. This rise is pressure ismeasured by the tissue chamber pressure sensor 506. At 604A, the rise intissue chamber pressure is calculated as a difference between thehighest tissue chamber pressure and lowest tissue chamber pressure foreach beat. In some embodiments, the tissue chamber pressure is sampledat a rate significantly higher than the number of beats/minute (e.g. at1 kHz for 60 bpm), such that multiple tissue chamber pressuremeasurements are taken prior to performing the calculation of tissuechamber pressure rise at 604A. For example, in some embodiments, thetissue chamber pressure is sampled at 610 Hz (i.e., 610 samples persecond).

As described above, the floor 393 of the canister 390 is a thin plateconfigured to undergo small deformations, such that its deflection dueto pressure/volume changes is linear and is a measure of the volumetriccompliance (defined as volume displaced per unit pressure change) of thecanister. In one embodiment, volumetric compliance of the canister 390is known and preprogrammed into the processor 502. In anotherembodiment, the processor 502 is configured to calculate volumetriccompliance in real-time. At 606, the volumetric change is calculated bymultiplying the calculated rise in canister pressure with theknown/estimated volumetric compliance of the canister 390.

At 608, the flow rate is calculated by dividing the calculated change involume by the beat period (i.e., a time interval between consecutivebeats, measured in units of time). An average of several consecutivevalues of flow rate or other calculated values can be displayed tominimize beat variations. For example, a moving average value can bedisplayed.

At 610, the resistance is calculated. Rresistance is expressed in unitsof pressure over flow rate, for example, mmHg/(mL/min). Flow rate iscalculated as described above. The resistance is calculated by theprocessor 502 based upon the calculated canister pressure rise,calculated at 604A, and a measured chamber pressure, at 604B. Thecalculated canister pressure rise and measured chamber pressure can bebased on substantially simultaneous and relatively high rate sampling ofthe pressure on each side of the tissue (i.e. at both the tissue chambersensor 506 and the pumping chamber sensor 510). In some embodiments, thesampling rate is significantly higher than the number of beats perminute. For example, the pressures at the sensors 506, 510 can besampled 1,000 times per second (1 kHz). As the oxygen pressure in thepumping chamber 325 rises, the pressure in the canister 390 rises at aslower rate. For improved accuracy, pressure can be measured at a highrate and accumulated for each beat period. For example, the totalpressure impulse for each beat can be integrated step-wise. Furtheraveraging or other statistical analysis can be performed by theprocessor 502 to reduce error. Due to the low operating pressures of theapparatus, a resistance to flow can be approximated by laminar flow,such that instantaneous flow rate is proportional to the instantaneouspressure drop. Calculations can be performed in real-time using directpressure measurements.

An apparatus 700 according to an embodiment is illustrated in FIGS.19-29. The apparatus 700 is configured to oxygenate a perfusate and toperfuse a tissue for extracorporeal preservation of the tissue. Unlessstated otherwise, the apparatus 700 can be similar in many respects(e.g., form and/or function) to the apparatus described herein (e.g.,apparatus 10, 100, 300), and can include components similar in manyrespects (e.g., form and/or function) to components of the apparatusdescribed herein. The apparatus 700 includes a lid assembly 710, acanister 790, and a coupling mechanism 850.

The lid assembly 710 defines a chamber 724 (see, e.g., FIG. 25)configured to receive components of a pneumatic system (not shown), suchas the pneumatic system 200 described above, and/or a control system(not shown), such as the control system 500 described above. In someembodiments, the chamber 724 is formed by a lid 720 of the lid assembly710. In some embodiments, the chamber 724 can be formed between a lowerportion 723 of the lid 720 and an upper portion 722 of the lid.

Retelling to FIGS. 20 and 21A, the lid assembly 710 defines a pumpingchamber 725 configured to receive oxygen (e.g., from the pneumaticsystem), to facilitate diffusion of the oxygen into a perfusate (notshown) and to facilitate movement of the oxygenated perfusate into atissue (not shown). A top of the pumping chamber 725 is formed by alower portion 728 of a membrane frame 744 of the lid assembly 710. Abottom of the pumping chamber 725 is formed by an upper surface 734 of abase 732 of the lid assembly 710.

As illustrated in FIGS. 20-24, the lid assembly 710 includes a firstgasket 742, a membrane 740, and the membrane frame 744. The membrane 740is disposed within the pumping chamber 725 and divides the pumpingchamber 725 into a first portion 727 and a second portion 729 differentthan the first portion. The first gasket 742 is disposed between themembrane 740 and the membrane frame 744 such that the first gasket isengaged with an upper surface 741 of the membrane 740 and a lower,perimeter portion of the membrane frame 744 (see, e.g., FIG. 24). Thefirst gasket 742 is configured to seal a perimeter of the first portion727 of the pumping chamber 725 twined between the lower portion 728 ofthe membrane frame 744 and the upper surface 741 of the membrane 740. Inother words, the first gasket 742 is configured to substantially preventlateral escape of oxygen from the first portion 727 of the pumpingchamber 725 to a different portion of the pumping chamber. In theembodiment illustrated in FIG. 24, the first gasket 742 has a perimetersubstantially similar in shape to a perimeter defined by the membrane740 (e.g., when the membrane is disposed on the membrane frame 744). Inother embodiments, however, a first gasket can have another suitableshape for sealing a first portion of a pumping chamber configured toreceive oxygen from a pneumatic system.

The first gasket 742 can be constructed of any suitable material. Insome embodiments, for example, the first gasket 742 is constructed ofsilicone, an elastomer, or the like. The first gasket 742 can have anysuitable thickness. For example, in some embodiments, the first gasket742 has a thickness within a range of about 0.1 inches to about 0.15inches. More specifically, in some embodiments, the first gasket 742 hasa thickness of about 0.139 inches. The first gasket 742 can have anysuitable level of compression configured to maintain the seal about thefirst portion 727 of the pumping chamber 725 when the components of thelid assembly 710 are assembled. For example, in some embodiments, thefirst gasket 742 is configured to be compressed by about 20 percent.

The membrane 740 is configured to permit diffusion of gas (e.g., oxygen)from the first portion 727 of the pumping chamber 725 through themembrane to the second portion 729 of the pumping chamber, and viceversa. The membrane 740 is configured to substantially prevent a liquid(e.g., the perfusate) from passing through the membrane. In this manner,the membrane 740 can be characterized as being semi-permeable. Themembrane frame 744 is configured to support the membrane 740 (e.g.,during the oxygenation of the perfusate and perfusion of the tissue).The membrane frame 744 can have a substantially round or circular shapedperimeter. The membrane frame 744 includes a first port 749A and asecond port 749B. The first port 749A is configured to convey fluidbetween the first portion 727 of the pumping chamber and the pneumaticsystem (not shown). For example, the first port 749A can be configuredto convey oxygen from the pneumatic system to the first portion 727 ofthe pumping chamber 725. The second port 749B is configured to permit apressure sensor line (not shown) to be disposed therethrough. Thepressure sensor line can be, for example, polyurethane tubing. The ports749A, 749B can be disposed at any suitable location on the membraneframe 744, including, for example, towards a center of the membraneframe 744 as shown in FIG. 21A. Although the ports 749A, 749B are shownin close proximity in FIG. 21A, in other embodiments, the ports 749A,749B can be differently spaced (e.g., closer together or further apart).

Referring to FIGS. 22-24, at least a portion of the membrane 740 isdisposed (e.g., wrapped) about at least a portion of the membrane frame744. In some embodiments, the membrane 740 is stretched when it isdisposed on the membrane frame 744. The membrane 740 is disposed about alower edge or rim of the membrane frame 744 and over at least a portionof an outer perimeter of the membrane frame 744 such that the membrane740 is engaged with a series of protrusions (e.g., protrusion 745)configured to help retain the membrane with respect to the membraneframe. The membrane frame 744 is configured to be received in a recess747 defined by the lid 720 (see, e.g., FIG. 21A). As such, the membrane740 is engaged between the membrane frame 744 and the lid 720, whichfacilitates retention of the membrane with respect to the membraneframe. In some embodiments, the first gasket 742 also helps to maintainthe membrane 740 with respect to the membrane frame 744 because thefirst gasket is compressed against the membrane between the membraneframe 744 and the lid 720.

As illustrated in FIG. 20, the membrane 740 is disposed within thepumping chamber 725 at an angle with respect to a horizontal axis A4. Inthis manner, the membrane 740 is configured to facilitate movement offluid towards a purge port 706 in fluid communication with the pumpingchamber 725, as described in more detail herein. The angle of incline ofthe membrane 740 can be of any suitable value to allow fluid (e.g., gasbubbles, excess liquid) to flow towards the purge port 706 and exit thepumping chamber 725. In some embodiments, the angle of incline isapproximately in the range of 1°-10°, in the range of 2°-6°, in therange of 2.5°-5°, in the range of 4°-5° or any angle of incline in therange of 1°-10° (e.g., approximately 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°,10°). More specifically, in some embodiments, the angle of incline isapproximately 5°.

The membrane 740 can be of any suitable size and/or thickness,including, for example, a size and/or thickness described with respectto another membrane herein (e.g., membrane 40, 140, 340). The membrane740 can be constructed of any suitable material. For example, in someembodiments, the membrane is constructed of silicone, plastic, oranother suitable material. In some embodiments, the membrane isflexible. As illustrated in FIG. 23, the membrane 740 can besubstantially seamless. In this manner, the membrane 740 is configuredto be more resistant to being torn or otherwise damaged in the presenceof a flexural stress caused by a change in pressure in the pumpingchamber due to the inflow and/or release of oxygen or another gas.

Referring to FIG. 20, the lid 720 includes the purge port 706 disposedat the highest portion of the pumping chamber 725 (e.g., at the highestportion or point of the second portion 729 of the pumping chamber 725).The purge port 706 is configured to permit movement of fluid from thepumping chamber 725 to an area external to the apparatus 700. The purgeport 706 can be similar in many respects to a purge port describedherein (e.g., port 78, purge ports 106, 306).

As noted above, the upper surface 734 of the base 732 forms the bottomportion of the pumping chamber 725. Referring to FIGS. 21A and 26, alower surface 736 of the base 732 forms an upper portion of a tissuechamber 792. The tissue chamber 792 is formed by the canister 790 andthe lower surface 736 of the base 732 when the lid assembly 710 iscoupled to the canister 790. A well 758 is extended from the lowersurface 736 of the base 732 (e.g., into the tissue chamber 792). Thewell 758 is configured to contain a sensor (not shown) configured todetect the temperature within the tissue chamber 792. The well 758 canbe configured to substantially fluidically isolate the sensor from thetissue chamber 792, thereby preventing liquid (e.g., perfusate) from thetissue chamber from engaging the sensor directly. In some embodiments,the sensor contained in the well 758 can be in electrical communicationwith a control unit (such as control unit 500, described in detailabove).

The lower surface 736 of the base 732 defines a first concavely inclinedportion 751 and a second concavely inclined portion 753 different fromthe first portion 751. Said another way, the portions of the base 732forming each of the first portion 751 and the second portion 753 of thelower surface 736 lie along a plane having an axis different than thehorizontal axis A4. For example, each of the first portion 751 and thesecond portion 753 of the base can be in the shape of an inverted cone.The portions of the lower surface 736 of the base forming the first andsecond portions 751, 753 can each be inclined with respect to thehorizontal axis A4 at an angle equal to or greater than about 5°. Eachof the first portion 751 and the second portion 753 of the lower surface736 of the base 732 define the highest points or portions (i.e., thepeak(s)) of the tissue chamber 792 when the apparatus 700 is in anupright position (as shown in FIG. 20). In this manner, the base 732 isconfigured to facilitate movement of fluid towards the highestportion(s) of the tissue chamber 792 as the tissue chamber 792 is filledwith fluid approaching a maximum volume or maximum fluid capacity of thetissue chamber.

As illustrated in FIG. 21A, valves 738A, 738B, respectively, aredisposed at approximately the peak of each of the first portion 751 andthe second portion 753, respectively, of the base 732. Because valves738A, 738B are substantially similar in form and function, only valve738A is described in detail herein. The valve 738 is moveable between anopen configuration and a closed configuration. In its openconfiguration, the valve 738A is configured to permit movement of fluidfrom the tissue chamber 792 to the pumping chamber 725 via the valve.Specifically, the valve 738A is configured to permit fluid to move fromthe tissue chamber 792 into the second portion 729 of the pumpingchamber 725. In this manner, an excess amount of fluid within the tissuechamber 792 can overflow through the valve 738A and into the pumpingchamber 725. In its closed configuration, the valve 738A is configuredto substantially prevent movement of fluid from the pumping chamber 725to the tissue chamber 792, or vice versa, via the valve. The valve 738Ais moved from its closed configuration to its open configuration when apressure in the tissue chamber 792 is greater than a pressure in thepumping chamber 725. In some embodiments, the valve 738A is moved fromits open position to its closed position when a pressure in the pumpingchamber 725 is greater than a pressure in the tissue chamber 792. Insome embodiments, the valve 738A is biased towards its closedconfiguration.

The valve 738A can be a ball check valve. The valve 738A is moveablebetween a closed configuration in which a ball of the valve 738A isdisposed on a seat of the valve and an open configuration in which theball is lifted off of the seat of the valve. The ball of the valve 738Ais configured to rise off of the seat of the valve when the pressure inthe tissue chamber 792 is greater than the pressure in the pumpingchamber 725. In some embodiments, the membrane 740 is positioned inproximity over the valve 738A to prevent the ball from rising too highabove the seat such that the ball could be laterally displaced withrespect to the seat. The valves 738A, 738B can be similar in manyrespects to a valve described herein (e.g., valve 138, 338A, 338B). Forexample, the valves 738A, 738B can include a jet 760A, 760B,respectively, similar in form and/or function as the jets 360A, 360Bdescribed in detail above with respect to apparatus 300. As such, thevalves 738A, 738B are not described in more detail herein.

The base 732 is coupled to the lid 720. In some embodiments, the base732 and the lower portion 723 of the lid 720 are coupled together, e.g.,about a perimeter of the pumping chamber 725 (see, e.g., FIGS. 21A and25). The base 732 and the lid 720 can be coupled using any suitablemechanism for coupling including, but not limited to, a plurality ofscrews, an adhesive, a glue, a weld, another suitable couplingmechanism, or any combination of the foregoing. A gasket 748 is disposedbetween the base 732 and the lid 720 (see e.g., FIGS. 20 and 21A). Thegasket 748 is configured to seal an engagement of the base 732 and thelid 720 to substantially prevent fluid in the pumping chamber 725 fromleaking therebetween. In some embodiments, the gasket 748 is an O-ring.The gasket 748 can be similar in many respects to a gasket describedherein (e.g., gasket 148, 742).

The base 732 defines a lumen 735 configured to be in fluid communicationwith a lumen 774 of a tissue adapter 770, described in more detailbelow. The base 732 is configured to permit oxygenated perfusate to movefrom the pumping chamber 725 through its lumen 735 into the lumen 774 ofthe tissue adapter 770 towards the tissue chamber 792. In this manner,the lumen 735 of the base 732 is configured to help fluidically couplethe pumping chamber 725 and the tissue chamber 792.

The tissue adapter 770 is configured to substantially retain the tissuewith respect to the apparatus 700. The tissue adapter 770 can be similarin many respects to an adapter described herein (e.g., adapter 26,tissue adapter 170). Referring to FIG. 21B, the tissue adapter 770includes a handle portion 778, an upper portion 772, and a lower portion780, and defines the lumen 774 extended therethrough. The upper portion772 of the tissue adapter 770 is extended from a first side of thehandle portion 778. The lower portion 780 of the tissue adapter 770 isextended from a second side of the handle portion 778 different than thefirst side of the handle portion. In some embodiments, the lower portion780 is configured to be at least partially inserted into the tissue.More specifically, at least a portion of the lower portion 780 isconfigured to be inserted into a vessel (e.g., an artery, a vein, or thelike) of the tissue. For example, the protrusion 780 can be configuredto be at least partially received in a bodily vessel having a diameterwithin the range of about 3 millimeters to about 8 millimeters. In otherembodiments, the lower portion 780 is configured to be coupled to thetissue via an intervening structure (not shown in FIG. 21B) tofluidically couple the lumen 774 of the tissue adapter 770 to a vesselof the tissue. The intervening structure can be, for example, silasticor other tubing. In this manner, the lower portion 780 is configured todeliver the fluid (e.g., the oxygenated perfusate) from the pumpingchamber 725 to the vessel of the tissue via the lumen 774 defined by thetissue adapter 770. The vessel of the tissue can be sutured to the lowerportion 780 of the adapter 770 and/or to the intervening structure(e.g., tubing).

The upper portion 772 of the tissue adapter 770 is configured to couplethe tissue adapter to the base 732 of the lid assembly 710. The upperportion 772 of the tissue adapter is configured to be received by thelumen 735 defined by the base. The upper portion 772 includes a firstprojection 776A and a second projection 776B spaced apart from the firstprojection. The projections 776A, 776B of the tissue adapter 770 areconfigured to be received by the lumen 735 of the base 732 in opposingspaces between a first protrusion 754 and a second protrusion 756 (shownin FIG. 21B) disposed within the lumen of the base. Once the upperportion 772 is received in the lumen 735 of the base 732, the tissueadapter 770 can be rotated approximately ninety degrees such that itsfirst projection 776A and its second projection sit on a shoulder 755,757, respectively, defined by the protrusions 754, 756, respectively, ofthe base. The tissue adapter 770 can be rotated in either a clockwise ora counterclockwise direction to align its projections 776A, 776B withthe shoulders 755, 757 of the protrusions 754, 756 of the base 732.Similarly, the tissue adapter 770 can be rotated in either the clockwiseor the counterclockwise direction to unalign its projections 776A, 776Bwith the shoulders 755, 757 of the protrusions 754, 756 of the base 732,such as for decoupling of the adapter from the base. Said another way,the tissue adapter 770 can be configured to be coupled to the base 732with a bayonet joint. The handle portion 778 is configured to facilitatecoupling and decoupling of the tissue adapter 770 and the base 732. Forexample, the handle portion 778 is configured to be grasped by a hand ofan operator of the apparatus 700. The handle portion 778 can besubstantially disc-shaped, and includes a series of recesses configuredto facilitate grasping the handle portion with the operator's handand/or fingers.

In some embodiments, the upper portion 772 of the tissue adapter 770includes a set of protrusions spaced apart (e.g., vertically offset)from projections 776A, 776B. For example, as shown in FIG. 21B,protrusions 777A, 777B are disposed at opposing portions of an outerperimeter of the upper portion 772 of the tissue adapter 770. Theprotrusions 777A, 777B can each be configured to be received in a recess779A, 779B, respectively, defined by the base 732. In some embodiments,the protrusions 777A, 777B are configured to retain a gasket 788disposed about the upper portion 772 of the tissue adapter 770 betweenthe handle portion 778 of the adapter and the base 732. The gasket 788is configured to substantially prevent a fluid from flowing between thepumping chamber 725 and the tissue chamber 792 within a channel formedbetween an outer surface of the upper portion 772 of the tissue adapter770 and an inner surface of the lumen 735 of the base 732. In someembodiments, the gasket 788 is compressed between the tissue adapter 770and the base 732 when the tissue adapter is coupled to the base. Thegasket 788 can be similar in many respects to a gasket described herein(e.g., gasket 188, 742).

In some embodiments, at least a portion of the lid assembly 710 isconfigured to minimize flexure of the portion of the lid assembly, suchas may occur in the presence of a positive pressure (or pulse wave)caused by introduction of oxygen into the pumping chamber 725 and/or ofoxygenated perfusate into the tissue chamber 792. For example, asillustrated in FIG. 21A, an upper portion 722 of the lid 720 includes aplurality of ribs 726 configured to minimize flexure of the lid 720 inresponse to externally applied loads, for example, if an operatorpresses down on the lid 720. In other words, the plurality of ribs 726structurally reinforces the lid 720 to help prevent the lid 720 fromflexing. In another example, as illustrated in FIG. 22, an upper portionof the membrane frame 744 can include ribs 746 configured to reinforcethe top of the pumping chamber 725 to help prevent flexure of the top ofthe pumping chamber 725 during pumping of oxygen through the lidassembly 710. In yet another example, the base 732 is configured tosubstantially minimize flexure of the base, such as may occur in thepresence of a positive pressure caused by the introduction of oxygeninto the pumping chamber 725 and/or of oxygenated perfusate into thetissue chamber 792. As illustrated in FIG. 25, the base 732 includes aplurality of ribs 731 extended from its upper surface. The plurality ofribs 731 is configured to reinforce the base 732, which helps tominimize flexure of the base. The plurality of ribs (e.g., ribs 726,746, and/or 731) can be in any suitable configuration, including, forexample, a circular configuration, a hub-and-spoke combination, aparallel configuration, or the like, or any suitable combinationthereof. For example, as shown in FIGS. 21A, 22 and 25, the plurality ofribs (e.g., ribs 726, 746, 731) are a combination of circular andhub-and-spoke configurations.

Referring to FIG. 20, the lid assembly 710 includes a fill port 708configured to permit introduction of a fluid (e.g., the perfusate) intothe tissue chamber 792 (e.g., when the lid assembly 710 is coupled tothe canister 790). The fill port 708 can be similar in many respects toa port described herein (e.g., port 74, fill port 108). In theembodiment illustrated in FIG. 20, the fill port 708 includes a fitting707 coupled to the lid 720 and defines a lumen 709 in fluidiccommunication with a lumen 737 defined by the base 732, which lumen 737is in fluidic communication with the tissue chamber 792. The fitting 707can be any suitable fitting, including, but not limited to, a luer lockfitting. The fill port 708 can include a cap 705 removably coupled tothe port. The cap 705 can help prevent inadvertent movement of fluid,contaminants, or the like through the fill port 708.

The lid assembly 710 is configured to be coupled to the canister 790.The lid assembly 710 includes handles 712, 713. The handles 712, 713 areeach configured to facilitate coupling the lid assembly 710 to thecanister 790, as described in more detail herein. Said another way, thehandles 712, 713 are configured to move between a closed configurationin which the handles prevent the lid assembly 710 being uncoupled orotherwise removed from the canister 790, and an open configuration inwhich the handles do not prevent the lid assembly 710 from beinguncoupled or otherwise removed from the canister. The handles 712, 713are moveably coupled to the lid 720. Each handle 712, 713 can bepivotally coupled to opposing sides of the coupling mechanism 850(described in more detail herein) disposed about the lid 720. Forexample, each handle 712, 713 can be coupled to the coupling mechanism850 via an axle (not shown). Each handle includes a series of gear teeth(not shown) configured to engage a series of gear teeth 719 (see, e.g.,FIG. 25) disposed on opposing sides of the lid 720 as the handles 712,713 each pivot with respect to the coupling mechanism 850, thus causingrotation of the coupling mechanism 850, as described in more detailherein. In some embodiments, the handles 712, 713 include webbingbetween each tooth of the series of gear teeth, which is configured toprovide additional strength to the respective handle. In their closedconfiguration, the handles 712, 713 are substantially flush to thecoupling mechanism 850. In some embodiment, at least one handle 712 or713 includes an indicia 713B indicative of proper usage or movement ofthe handle. For example, as shown in FIG. 28C, the handle 713 includesindicia (i.e., an arrow) indicative of a direction in which the handleportion can be moved. As also shown in FIG. 28C, in some embodiments,the handles 712, 713 include a ribbed portion configured to facilitate agrip by a hand of an operator of the apparatus 700.

The canister 790 can be similar in many respects to a canister describedherein (e.g., canister 32, 190, 390). As shown in FIG. 29, the canister790 includes a wall 791, a floor (also referred to herein as “bottom”)793, and a compartment 794 defined on its sides by the wall and on itsbottom by the floor. The compartment 794 can form a substantial portionof the tissue chamber 792.

As shown in FIGS. 27A-27C, at least a portion of the canister 790 isconfigured to be received in the lid assembly 710 (e.g., the base 732).The canister 790 includes one or more protruding segments 797 disposedadjacent, or at least proximate, to an upper rim 795 of the canister.Each segment 797 is configured to protrude from an outer surface of thecanister 790 wall 791. The segments 797 are configured to help properlyalign the canister 790 with the lid assembly 710, and to help couple thecanister 790 to the lid assembly 710. Each segment 797 is configured tobe received between a pair of corresponding segments 721 of the lid 720,as shown in FIG. 27B. A length L1 of the segment 797 of the canister 790is substantially equivalent to a length 1,2 (see, e.g., FIG. 27A) of anopening 860 between the corresponding segments 721 of the lid 720. Inthis manner, when the segment 797 of the canister 790 is received in thecorresponding opening of the lid 720, relative rotation of the canister790 and lid 720 with respect to each other is prevented. The canister790 can include any suitable number of segments 797 configured tocorrespond to openings between protruding segments 721 of the lid 720.For example, in the embodiment illustrated in FIG. 27B (and also shownin FIG. 29), the canister 790 includes ten segments 797, each of whichis substantially identical in form and function, spaced apart about theouter perimeter of the canister 790 adjacent the upper rim 795. In otherembodiments, however, a canister can include less than or more than tensegments.

A gasket 752 is disposed between the base 732 and the upper rim 795 ofthe wall 791 of the canister 790. The gasket 752 is configured to sealthe opening between the base 732 and the wall 791 of the canister 790 tosubstantially prevent flow of fluid (e.g., the perfusate) therethrough.The segments 797 of the canister 790 are configured to engage andcompress the gasket 752 when the canister 790 is coupled to the lid 720.The gasket 752 can be any suitable gasket, including, for example, anO-ring.

The floor 793 of the canister 790 is configured to flex when a firstpressure within the tissue chamber 792 changes to a second pressurewithin the tissue chamber, the second pressure different than the firstpressure. More specifically, in some embodiments, the floor 793 of thecanister 790 is configured to flex outwardly when a first pressurewithin the tissue chamber 792 is increased to a second pressure greaterthan the first pressure. For example, the floor 793 of the canister 790can be configured to flex in the presence of a positive pressure (or apulse wave) generated by the pumping of the oxygenated perfusate fromthe pumping chamber 725 into the tissue chamber 792, as described indetail above with respect to apparatus 100. In some embodiments, thefloor 793 of the canister 790 is constructed of a flexible membrane. Thefloor 793 of the canister 790 can have any suitable thickness T,including, for example, a thickness described above with respect tofloor 193 of canister 190. In some embodiments, the floor 793 has athickness T equal to or greater than 0.100 inches.

The canister 790 can be configured to enable an operator of theapparatus 700 to view the tissue when the tissue is sealed within thetissue chamber 792. In some embodiments, for example, at least a portionof the canister 790 (e.g., the wall 791) is constructed of a clear ortransparent material. In another example, in some embodiments, at leasta portion of the canister 790 (e.g., the wall 791) is constructed of atranslucent material. In yet another example, in some embodiments, acanister includes a window through which at least a portion of thetissue chamber can be viewed.

As noted above, the coupling mechanism 850 is configured to couple thecanister 790 to the lid assembly 710. In the embodiment illustrated inFIGS. 19-29, the coupling mechanism 850 is a retainer ring. The retainerring 850 is configured to be disposed about a lower rim of the lid 720and the upper rim 795 of the canister 790. An upper portion of theretainer ring 850 can be wrapped over a portion of the lid assembly 710(e.g., an upper perimeter edge of the base 732), as shown in FIG. 20. Inthis manner, compression of gasket 752 is improved when the lid assembly710 is coupled to the canister 790 by the retainer ring 850, asdescribed in more detail below. The retainer ring 850 can be of anysuitable size for being disposed about the lid 720 and the canister 790.For example, in some embodiments, the retainer ring 850 can be 22.35 cm(or about 8.80 inches) in diameter.

A plurality of segments 856 are extended from an inner surface of theretainer ring 850 at spaced apart locations about an inner perimeter ofthe retainer ring. Each segment of the plurality of segments 856 isconfigured to be aligned with a segment 721 of the lid 720 when theretainer ring 850 is coupled to the lid 720, and the handles 712, 713 ofthe lid assembly 710 are in the open configuration. In some embodiments,as shown in FIG. 27A, each segment of the plurality of segments 856 ofthe retainer ring 850 is configured to laterally abut an inner portionof an L-shaped portion of the corresponding segment 721 of the lid 720when the retainer ring 850 is disposed on the lid assembly 710 and thehandles 712, 713 of the lid assembly 710 are in the open configuration,which facilitates accurate alignment of the lid 720 and the retainerring 850. Accordingly, when the lid 720 and the retainer ring 850 arealigned and the handles 712, 713 of the lid assembly 710 are in the openconfiguration, the aligned segments 721 of the lid 720 and segments 856of the retainer ring 850 collectively define the openings 860 configuredto receive the segments 797 of the canister 790, described above.

To couple, or otherwise secure, the canister 790 to the lid assembly 710using the retainer ring 850, the handles 712, 713 of the lid assemblyare moved from their open configuration (see, e.g., FIGS. 27B and 28A)through an intermediate configuration (see, e.g., FIG. 28B) to theirclosed configuration (see, e.g., FIGS. 27C and 28C). As the handles 712,713 are moved from their open configuration towards their closedconfiguration, the retainer ring 850 is rotated in a first direction (asshown by arrow A1 in FIG. 28B) with respect to each of the canister 790and the lid assembly 710. Accordingly, as shown in FIG. 27C, when thehandles 712, 713 are in their closed configuration, the segments 856 ofthe retainer ring 850 are vertically aligned with the segments 797 ofthe canister 790, e.g., such that each segment of the retainer ring isdisposed beneath a corresponding segment 797 of the canister 790 whenthe apparatus 700 is in the upright position. Over-rotation of theretainer ring 850 with respect to the lid assembly 710 and the canister790 is prevented by an outer edge of the L-shaped portion of the lid 720segments 721. To decouple the lid assembly 710 from the canister 790,the handles 712, 713 are moved from their closed configuration to theiropen configuration, thus causing rotation of the retainer ring 850relative to the lid assembly and the canister in a second directionopposite the first direction. During decoupling, over rotation of theretainer ring 850 with respect to the lid assembly 710 and the canister790 is prevented because the segments 856 of the retainer ring will eachlaterally about the inner portion of the L-shaped portion of thecorresponding segment 721 of the lid 720.

As noted above, the apparatus 700 is configured for controlled deliveryof fluid (e.g., oxygen) from an external source (not shown) into thepumping chamber 725 of the lid assembly 710. The external source can be,for example, an oxygen cylinder. In some embodiments, the apparatus 700includes the pneumatic system, such as pneumatic system 200, configuredfor controlled venting of fluid (e.g., carbon dioxide) from the pumpingchamber 725 to an area external to the apparatus 700 (e.g., to theatmosphere). The pneumatic system 200 is moveable between a firstconfiguration in which the pneumatic system is delivering fluid to thepumping chamber 725 and a second configuration in which the pneumaticsystem is venting fluid from the pumping chamber 725. The pneumaticsystem 200 is described in detail above with respect to apparatus 100.

In use, the tissue is coupled to at least one of the tissue adapter 770or tubing configured to be coupled to the tissue adapter. The tissueadapter 770 can be coupled to the lid assembly 710. Optionally, adesired amount of perfusate can be disposed within the compartment 794of the canister 790 prior to disposing the lid assembly 710 on thecanister. For example, in some embodiments, a perfusate line (not shown)is connected to the tissue adapter 770 and the tissue is flushed withperfusate, thereby checking for leaks and partially filling the canister790 with perfusate. Optionally, when the canister 790 is substantiallyfilled, the perfusate line can be disconnected. The lid assembly 710 isdisposed on the canister 790 such that the tissue is received in thetissue chamber 792. The lid assembly 710 is coupled to the canister 790.Optionally, the lid assembly 710 and the canister 790 are coupled viathe retainer ring 850. Optionally, a desired amount of perfusate isdelivered to the tissue chamber 792 via the fill port 708. In someembodiments, a volume of perfusate greater than a volume of the tissuechamber 792 is delivered to the tissue chamber such that the perfusatewill move through the valves 738A, 738B into the second portion 729 ofthe pumping chamber 725.

A desired control scheme of the pneumatic system 200 is selected. Oxygenis introduced into the first portion 727 of the pumping chamber 725 viathe pneumatic system 200 based on the selected control scheme. Thepneumatic system 200 is configured to generate a positive pressure bythe introduction of oxygen into the first portion 727 of the pumpingchamber 725. The positive pressure helps to facilitate diffusion of theoxygen through the membrane 740. The oxygen is diffused through themembrane 740 into the perfusate disposed in the second portion 729 ofthe pumping chamber 725, thereby oxygenating the perfusate. Because theoxygen will expand to fill the first portion 727 of the pumping chamber725, substantially all of an upper surface 741 of the membrane 740 whichfaces the first portion of the pumping chamber can be used to diffusethe oxygen from the first portion into the second portion 729 of thepumping chamber.

As the tissue uses the oxygen, the tissue will release carbon dioxideinto the perfusate. Such carbon dioxide can be diffused from the secondportion 729 of the pumping chamber 725 into the first portion 727 of thepumping chamber 725. Carbon dioxide within the first portion 727 of thepumping chamber is vented via a control line (not shown) to a valve (notshown), and from the valve through a vent line (not shown) to theatmosphere external to the apparatus 700.

The positive pressure also causes the membrane 740 to flex, whichtransfers the positive pressure in the form of a pulse wave into theoxygenated perfusate. The pulse wave generated by the pumping chamber isconfigured to facilitate movement of the oxygenated perfusate from thesecond portion 729 of the pumping chamber 725 into the tissue via thetissue adapter 770 (and any intervening structure or tubing), thusperfusing the tissue. In some embodiments, the pumping chamber 725 isconfigured to generate a pulse wave in a similar manner as pumpingchamber 125, described in detail above with respect to apparatus 100.

At least a portion of the perfusate perfused through the tissue isreceived in the tissue chamber 792. In some embodiments, the pulse waveis configured to flow through the perfusate disposed in the tissuechamber 792 towards the floor 793 of the canister 790. The floor 793 ofthe canister 790 is configured to flex when engaged by the pulse wave.The floor 793 of the canister 790 is configured to return the pulse wavethrough the perfusate towards the top of the tissue chamber 792 as thefloor 793 of the canister 790 is returned towards its originalnon-flexed position. In some embodiments, the returned pulse wave isconfigured to generate a sufficient pressure to open the valves 738A,738B disposed at the highest positions in the tissue chamber 792. Inthis manner, the returned pulse wave helps to move the valves 738A, 738Bto their respective open configurations such that excess fluid (e.g.,carbon dioxide released from the tissue and/or the perfusate) can movethrough the valves from the tissue chamber 792 to the pumping chamber725. The foregoing perfusion cycle can be repeated as desired, includingin any manner described above with respect to other apparatus describedherein (e.g., apparatus 10, 100, 300).

Although the perfusion cycle has been described herein as including asubstantially regular intermittent pulse of oxygen from the pneumaticsystem 200 to the pumping chamber 725, in other embodiments, thepneumatic system 200 can be configured to deliver oxygen to the pumpingchamber 725 at a different interval (e.g., flow interval), such as thosevariations described above with respect to apparatus 100 and pneumaticsystem 200.

Although the lid assembly 710 has been illustrated and described asbeing configured for use with the canister 790, in other embodiments,the lid assembly 710 can be configured for use with canisters havingdifferent configurations. For example, although the canister 790 hasbeen illustrated and described herein as being of a certain size and/orshape, in other embodiments, a canister having any suitable dimensionscan be configured for use with the lid assembly 710. In someembodiments, for example, a first canister configured for use with thelid assembly 710 is dimensionally configured to accommodate a first typeof tissue, and a second canister configured for use with the lidassembly 710 is dimensionally configured to accommodate a second type oftissue different than the first type of tissue. For example, thecanister 790 illustrated in FIG. 29 and described herein with respect toapparatus 700 can be dimensioned to accommodate the first tissue, suchas a foot. The canister 790 can be, for example, a 2.7 liter cylindricalcanister having a height greater than or substantially equal to a widthof the floor 793. For example, as shown in FIG. 29, the compartment 794of the canister 790 can have a height H₁ of about 15 cm (or about 5.91inches) and a diameter D₁ of about 15 cm (note that diameter D₁ of thecompartment 794 can be different from a diameter D₃ of the top rim 795of the canister 790, which can be about 20 cm (or about 7.87 inches)).Accordingly, when the canister 790 is coupled to the lid assembly 710,the apparatus 700 can have an overall diameter of about 24 cm (or about9.44 inches) and an overall height of about 22.3 cm (or about 8.77inches).

In another embodiment, as illustrated in FIG. 30, a differentlydimensioned canister 990 can be used with the lid assembly 710. Thecanister 990 can be dimensioned to accommodate the second tissue, suchas a limb. The canister 990 can be, for example, a 3.0 liter cylindricalcanister having a wall 991 height less than a width of a floor 993 ofthe canister. For example, as shown in FIG. 30, the compartment 994 ofthe canister 990 can have a height 112 less than the height H₁ ofcanister 790 and a diameter D₂ greater than or equal to the diameter D₁i of canister 790. The height H₂ and diameter D₂ of the compartment 994can be such that the lid assembly 710 coupled to the canister 990 viathe retainer ring 850 collectively have an overall height of about 16.5cm (or about 6.48 inches) and a diameter of about 24 cm (or about 9.44inches). It should be noted that although specific dimensions aredescribed herein, in other embodiments, such dimensions can be differentand still be within the scope of the invention. The thickness of thefloor 993 of the canister 990 can be selected based on the height andwidth dimensions of the canister 990 to ensure that the floor 993 isconfigured to properly flex in the presence of the pulse wave, asdescribed above, and may be the same as or different than the thicknessof the floor 793 of canister 790. The canister 990 includes a pluralityof segments 997 protruding from an outer surface of the wall adjacent anupper rim 995 of the canister 990. The plurality of segments 997 areconfigured to facilitate coupling the canister 990 to the lid assembly710 and the retainer ring 850, as described above with respect to thecanister 790.

Referring to FIG. 31, in some embodiments, an apparatus includes abasket 870 configured to be disposed in a compartment 994 of thecanister 990. The basket 870 is configured to support the tissue (e.g.,limb, L) within the compartment 994. In some embodiments, for example,the basket 870 includes a bottom portion 872 on which the tissue can bedisposed. In some embodiments, the bottom portion 872 of the basket 870is smooth. The bottom portion 872 can be slightly curved to accommodatecurvature of the tissue. In some embodiments, netting (not shown) can beused to retain the tissue with respect to the basket 870 (e.g., when thetissue is disposed on the bottom portion 872 of the basket 870). Arms874A, 874B are disposed on a first side of the bottom portion 872 of thebasket 870 opposite arms 876A, 876B disposed on a second side of thebottom portion of the basket. Each pair of arms 874A, 874B and 876A,876B is extended vertically and terminates in a handle portion 875, 877,respectively, that couples the upper end portions of the arms.

In some embodiments, as shown in FIG. 31, a shape of the outer perimeterof the bottom portion 872 of the basket 870 can substantially correspondto a shape of a perimeter of the canister 990, such that outer edges oflower end portions of the arms 874A, 874B, 876A, 876B each abut an innersurface of the wall 991 of the canister. In this manner, lateralmovement of the basket 871, and thus of the tissue supported thereon, isprevented, or at least restricted. The handle portions 875, 877 can beconfigured to engage the lower surface 736 of the base 732 of the lidassembly 710 when the basket 870 is received in the canister's 990compartment 994 and the canister is coupled to the lid assembly 710. Inthis manner, vertical movement of the basket 870 with respect to thecanister 990 is prevented.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Where methods described above indicate certain eventsoccurring in certain order, the ordering of certain events may bemodified. For example, selecting the control scheme of the pneumaticsystem 200 can occur before the coupling the tissue to the tissueadapter 170, 770. Additionally, certain of the events may be performedconcurrently in a parallel process when possible, as well as performedsequentially as described above. Furthermore, although methods aredescribed above as including certain events, any events disclosed withrespect to one method may be performed in a different method accordingto the invention. Thus, the breadth and scope should not be limited byany of the above-described embodiments.

While the invention has been particularly shown and described withreference to specific embodiments thereof, it will be understood thatvarious changes in form and details may be made. For example, althoughthe valves 138, 738A, 738B disposed at the highest portion of the tissuechamber 192, 792 have been illustrated and described herein as being aball check valve, in other embodiments, a different type of valveconfigured to permit unidirectional flow of a fluid from the tissuechamber into the pumping chamber can be included in the apparatus. Forexample, in some embodiments, an apparatus includes a different type ofa check valve, such as a diaphragm check valve, a swing check valve, alife check valve, or the like. In another example, in some embodiments,an apparatus includes a valve that is different than a check valve.

Although the valve 210 of the pneumatic system 200 has been illustratedand described herein as being a solenoid valve, in other embodiments,the pneumatic system can include a different type of valve configured tocontrol the flow of oxygen into the pumping chamber.

Although the valve 210 of the pneumatic system 200 has been illustratedand described herein as including three ports, in other embodiments, avalve of a pneumatic system can include a different number of ports. Forexample, in some embodiments, the valve includes one, two, four, or moreports.

Although the pneumatic systems (e.g., pneumatic system 200, 220) havebeen illustrated and described as including a specific number of controlorifices (e.g., one control orifice 207 and two control orifices 223,225, respectively), in other embodiments, a pneumatic system can includeany suitable number of control orifices. For example, a pneumatic systemcan include one, two, three, four, or more control orifices.

Although the lid assemblies described herein (e.g., lid assembly 110,710) have been illustrated and described as being reinforced by aplurality of ribs (e.g., plurality of ribs 126, 131, 133, 726, 731)having a certain configuration (e.g., a parallel configuration or acombination circular/spoke and wheel configuration), in otherembodiments, the lid assembly can include a plurality of ribs having adifferent orientation. For example, in another embodiment, any of theplurality of ribs can have a grid configuration, a diamondconfiguration, a herringbone configuration, a spoke and wheelconfiguration, another suitable configuration, or any combination of theforegoing configurations. Additionally, although lid assembly 110 hasbeen illustrated and described herein as including a plurality of ribs(e.g., plurality of ribs 126, 131, 133) in a parallel configuration in afirst direction, in other embodiments, the plurality of ribs can have aparallel configuration in a different direction. For example, althoughthe plurality of ribs 131 are illustrated as having a parallelorientation in a first direction and the plurality of ribs 133 areillustrated as having a parallel orientation in a second directionsubstantially orthogonal to the first direction, in some embodiments,the plurality of ribs on each of an upper surface and a lower surface ofa base can be oriented in a different manner. For example, in someembodiments, a plurality of ribs on an upper surface of a base have aparallel orientation in a first direction and a plurality of ribs on alower surface of the base have a parallel orientation also in the firstdirection.

In another example, although the lid assemblies are illustrated anddescribed herein (e.g., lid assembly 110, 710) have been illustrated anddescribed as being reinforced by a plurality of ribs (e.g., plurality ofribs 126, 131, 133, 726, 731), in other embodiments, a lid assembly caninclude a different mechanism for reinforcement.

In some embodiments, an apparatus described herein can includecomponents in addition to those described above. For example, referringto FIG. 32, in some embodiments, the apparatus 700 includes a base 796configured to be coupled to the canister 790. In some embodiments, thecanister 790 and the base 796 are removably coupleable. The canister 790can be coupled to the base using any suitable coupling mechanism,including, for example, a resistance fit, mating threads, an adhesive,or other suitable coupling mechanism. In the embodiment illustrated inFIG. 32, an upper surface of the base 796 defines a recess 798configured to receive a bottom portion of the canister 790. The base 796is configured to provide stability to the canister 790 when the canister790 is coupled thereto and/or received in the recess 798 of the base796. In other words, the base 796 is configured to help maintain thecanister 790 in an upright position. In some embodiments, the base has awidth substantially equal to an overall width of the lid assembly 710.In this manner, the stability provided by the base 796 helps to off-setany top-heaviness imparted to the apparatus 700 by the lid assembly 710.The base 796 is also configured to protect the floor 793 of the canister790 when the floor 793 is flexed due to a pressure change within thetissue chamber 792, as described above.

In another example, the apparatus 700 can include a sterile carrierassembly 880, as illustrated in FIG. 33. The carrier assembly 880includes a top portion 882, a bottom portion 884 and a plurality oflatches 886 configured to couple the top portion 882 of the carrierassembly 880 to the bottom portion 884 of the carrier assembly 880. Thecarrier assembly 880 is configured to receive the apparatus 700 (i.e.,the coupled lid assembly 710, retainer ring 850 and canister 790) in acompartment (not shown) defined by the top and bottom portions 882, 884of the carrier assembly 880. The carrier assembly 880 is configured toprotect the apparatus 700 contained therein, including ensuring that thesterility of the apparatus 700 contained therein is not compromised whenthe apparatus 700 is removed from a sterile field. In this manner, thecarrier assembly 880 facilitates transportability of the apparatus 700.

In another example, in some embodiments, an apparatus described herein(e.g., apparatus 10, 100, 300, 700) includes at least one sensor (notshown) configured to detect information associated with the tissue, suchas a measurement associated with the tissue. For example, the apparatusmay comprise oxygen sensors allowing the apparatus to determine anoxygen consumption rate for the tissue. The apparatus can include adisplay configured to display an output based on the informationdetected by the at least one sensor. For example, in some embodiments,the lid 112 of the lid assembly 110 includes a display configured todisplay a message in real-time based on a measurement associated withthe tissue detected by the at least one sensor. The lid 112 of the lidassembly 110 may also include an indicator of the health of the tissuebased upon the measurements from the sensors.

Although various embodiments have been described as having particularfeatures and/or combinations of components, other embodiments arepossible having any combination or sub-combination of any featuresand/or components from any of the embodiments described herein. Thespecific configurations of the various components can also be varied.For example, the size and specific shape of the various components canbe different than the embodiments shown, while still providing thefunctions as described herein. Thus, the breadth and scope of theinvention should not be limited by any of the above-describedembodiments. The previous description of the embodiments is provided toenable any person skilled in the art to make or use the invention. Whilethe invention has been particularly shown and described with referenceto embodiments thereof, it will be understood by those skilled in theart that various changes in form and details may be made therein withoutdeparting from the spirit and scope of the invention.

Incorporation by Reference

References and citations to other documents, such as patents, patentapplications, patent publications, journals, books, papers, webcontents, have been made throughout this disclosure. All such documentsare hereby incorporated herein by reference in their entirety for allpurposes.

Equivalents

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The foregoingembodiments are therefore to be considered in all respects illustrativerather than limiting on the invention described herein. Scope of theinvention is thus indicated by the appended claims rather than by theforegoing description, and all changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein.

The invention claimed is:
 1. A portable apparatus for preserving severedtissue, comprising: a tissue chamber; and a lid assembly configured tomate with the tissue chamber, the lid assembly comprising: a pumpingchamber having a semi-permeable membrane disposed at an inclined anglewith respect to horizontal when the lid assembly and tissue chamber aremated and placed on a horizontal surface, the semi-permeable membranebeing configured to push against a preservation fluid and cause thepreservation fluid to perfuse a severed tissue in the tissue chamberwith oxygenated preservation fluid at a pressure greater thanatmospheric pressure; a fill port defining a lumen having a firstopening and a second opening, wherein the first opening opens to theexterior of the lid assembly and the second opening opens to the tissuechamber; and a purge port connecting the exterior of the lid assembly tothe pumping chamber, thus allowing the apparatus to self-purge a fluidfrom the tissue chamber when the tissue chamber and lid assembly aremated, and the tissue chamber is filled with a liquid via the fill port.2. The apparatus of claim 1, wherein the membrane is disposed within thelid assembly at an angle such that when the lid assembly and the tissuechamber are mated and placed on a horizontal surface the membrane candirect a rising fluid toward the purge port.
 3. The apparatus of claim2, wherein the purge port is configured to permit the rising fluid toflow to an external area.
 4. The apparatus of claim 2, wherein themembrane is inclined at an angle of approximately 1° -10° with respectto a line perpendicular to gravity when the apparatus is used totransport severed tissue.
 5. The apparatus of claim 2, wherein themembrane flexes in response to a pressure increase in the first portionof the pumping chamber, thereby exerting a pressure against thepreservation fluid.
 6. The apparatus of claim 1, wherein the lidassembly is removably coupleable to the tissue chamber.
 7. The apparatusof claim 2, wherein the lid assembly comprises a pneumatic systemconfigured to generate a positive pressure in the first portion of thepumping chamber.
 8. The apparatus of claim 1, wherein the fluid ispreservation fluid.
 9. The apparatus of claim 1, wherein the fluid is agas.
 10. The apparatus of claim 1, wherein the apparatus is capable ofself-purging a fluid while perfusing the severed tissue.
 11. Theapparatus of claim 1, further comprising a basket or sling to receivethe severed tissue.
 12. The apparatus of claim 1, wherein the apparatusis capable of regulating the pressure of the preservation fluid byself-purging the preservation fluid.
 13. The apparatus of claim 1,wherein the purged fluid is directed to an external area.
 14. Theapparatus of claim 2, wherein the rising fluid is a gas.